Continuing Education Activity

Turner syndrome is a chromosomal disorder caused by the partial or complete absence of one X chromosome, most commonly in phenotypic females. The condition arises from meiotic nondisjunction or structural abnormalities of the X chromosome and occurs sporadically, without established environmental risk factors or association with advanced parental age. Disruption of X-chromosome material impairs normal growth and gonadal development, leading to characteristic features such as short stature, delayed puberty, primary amenorrhea, and neonatal lymphedema, as well as physical findings including a webbed neck and low-set ears. Diagnosis is confirmed by karyotype analysis, often initiated after recognition of growth delay or distinctive phenotypic features. Management requires lifelong monitoring because of risks of infertility, cardiovascular disease, hypertension, and autoimmune disorders.

This educational activity equips clinicians with the knowledge needed to recognize, diagnose, and manage Turner syndrome across the lifespan. Participants gain insight into the condition's genetic basis, clinical manifestations, diagnostic strategies, and evidence-based treatment approaches, including growth hormone therapy, estrogen replacement, and surveillance for associated comorbidities. Emphasis is placed on early identification and longitudinal care to improve health outcomes. Collaboration within an interprofessional team, including endocrinology, cardiology, genetics, and primary care, enhances coordinated screening, timely intervention, and comprehensive support, ultimately optimizing quality of life and long-term outcomes for individuals with Turner syndrome.

Objectives:

• Interpret genetic testing results, imaging studies, and laboratory data relevant to the diagnosis and management of Turner syndrome.
• Implement personalized, evidence-based management strategies for Turner syndrome to address potential complications and reduce their burden.
• Improve patients' understanding of the causes, associated health risks, and available therapies for Turner syndrome to support informed decision-making and long-term care planning.
• Collaborate with the interprofessional team to educate, treat, and monitor individuals with Turner syndrome to improve health outcomes.

Introduction

Otto Ullrich, a German pediatrician, first described the complete clinical phenotype of Turner syndrome in an 8-year-old girl in 1930. In 1938, Henri Turner, an Oklahoma physician, independently reported similar findings.[1] The disorder subsequently became known as Turner syndrome and is also referred to as Ullrich–Turner syndrome.

Turner syndrome is a sex chromosome disorder affecting individuals with a female phenotype who have one intact X chromosome and a partial or complete absence of the second sex chromosome. The chromosomal basis (45,X) was first identified by the British researcher Charles E. Jones in 1959, and Turner syndrome is the most common sex chromosome abnormality occurring in girls and women.[2]

Traditional diagnosis relies on identifying specific phenotypic features, such as a characteristic facial appearance, neck webbing, and peripheral lymphedema (see Image: Girl with Turner Syndrome). More recently, the recognized clinical manifestations of Turner syndrome have expanded to include, either alone or in combination, short stature, premature ovarian insufficiency (including delayed puberty), early sensorineural hearing loss, congenital cardiovascular, skeletal, and renal anomalies, a distinctive neurodevelopmental profile, and a higher prevalence of autoimmune conditions, such as autoimmune thyroiditis and celiac disease.[3][4]

Etiology

Turner syndrome is almost always caused by a de novo chromosomal abnormality that arises randomly during the formation of reproductive cells or in early embryonic development, resulting in one intact X chromosome and the complete or partial absence of the second sex chromosome. The recurrence risk for phenotypically normal parents who have a child with Turner syndrome is extremely low. In rare cases, when a parent has a partial deletion of an X chromosome, Turner syndrome can be passed from one generation to the next. This is the only scenario in which Turner syndrome could be considered "inherited," and it accounts for a very small minority of cases. [National Library of Medicine (US). MedlinePlus. Bethesda (MD): National Library of Medicine (US); Turner syndrome. Available from: https://medlineplus.gov/genetics/condition/turner-syndrome/]

The types and frequencies of karyotypes associated with Turner syndrome are summarized in Table 1.

Table

Table 1. Types and Frequencies of Karyotypes Associated with Turner Syndrome.

Turner syndrome in phenotypic males is extremely rare but well documented, occurring almost exclusively in those with 45,X/46,XY mosaicism. Its true prevalence is difficult to determine, but it represents a small subset of all 45,X/46,XY cases. Approximately 40% to 53% of patients with this karyotype are raised as males, though many may remain undiagnosed if clinical features are subtle.[5]

There are a few instances of X chromosome abnormalities in which the diagnosis of Turner syndrome does not apply. First, individuals with small distal deletions of the short arm of the X chromosome (Xp22.33), which contains the short stature homeobox (SHOX) gene, often exhibit short stature and other skeletal anomalies associated with SHOX deletion. However, these patients generally do not present with hallmark features of Turner syndrome, such as an increased risk for cardiac anomalies, neurocognitive issues, or ovarian insufficiency. Second, individuals with deletions distal to Xq24 frequently experience primary or secondary amenorrhea but lack other typical features of Turner syndrome, such as short stature. These cases should be classified as premature ovarian insufficiency rather than Turner syndrome. Finally, women older than 50 with less than 5% mosaicism for the 45,X karyotype are not considered to have Turner syndrome because low-level 45,X mosaicism at this frequency represents age-related loss of the X chromosome, a normal phenomenon, rather than a pathological chromosomal abnormality present from conception or early development.[6][7]

Epidemiology

Turner syndrome occurs in approximately 1 in 2000 to 1 in 2500 live female births.[8] A recent nationwide database estimated the prevalence at 3.2 per 10,000 female live births (95% confidence interval= 3.0–3.3) across all pregnancy outcomes, and at 1.9 per 10,000 live births when only live births and stillbirths were considered.[9] Prevalence during the prenatal period is substantially higher, as more than 99% of fetuses with a 45,X karyotype result in spontaneous pregnancy loss, usually before 28 weeks of gestation.

Increased awareness and use of prenatal ultrasound scans have contributed to a decline in the prevalence at birth, largely because some mothers carrying fetuses diagnosed with Turner syndrome elect to terminate the pregnancy. However, the true prevalence is unknown because many patients with a mild phenotype remain undiagnosed or receive a diagnosis later in adulthood.[10] Results from a nationwide study identified 3 peaks in age at diagnosis: younger than 1 year (14.9%), adolescence (ages 10–17) (33.2%), and adulthood (38.5%). The median age at diagnosis was approximately 15 years, reflecting diagnostic delays during infancy and early childhood.[11]

Pathophysiology

The pathophysiology of Turner syndrome reflects the consequences of X chromosome monosomy or structural abnormalities that result in reduced dosage of genes essential for normal development. Loss of one copy of genes that normally escape X-inactivation—particularly those within the pseudoautosomal regions—leads to haploinsufficiency and affects multiple organ systems, leading to hypogonadotropic hypogonadism, short stature, cardiovascular and vascular abnormalities, liver disease, renal abnormalities, neurocognitive abnormalities, and skeletal problems.[12] The clinical phenotype varies substantially depending on the specific karyotype and the proportion of affected cells, underscoring the complex relationship between chromosomal constitution and organ-specific manifestations.

Monosomy X (45,X), the most common karyotype in Turner syndrome, is characterized by the complete absence of an X chromosome in all cells and typically arises as a random event during the formation of reproductive cells in one parent. This error in cell division, known as nondisjunction, can produce reproductive cells with an abnormal number of chromosomes. For example, nondisjunction may result in the loss of a sex chromosome from either an oocyte or a sperm. If such a gamete contributes to conception, the resulting individual will have a single X chromosome in all cells, lacking the second sex chromosome (see Image. Turner Syndrome Karyotype).

Other chromosomal variations can cause Turner syndrome in addition to the 45,X karyotype. Mosaic Turner syndrome, in which some cells contain 45,X and others 46,XX, 46,XY, or other rare karyotypes, is a relatively common variant (please refer to the Etiology section for more information). Isochromosome and ring chromosome variants, which involve loss of critical portions of the X chromosome, are less common causes of Turner syndrome. Mosaic Turner syndrome arises from a random event during early fetal cell division. Consequently, some cells contain the usual 2 sex chromosomes, whereas others carry only 1 copy of the X chromosome.

The clinical features of Turner syndrome arise from the loss of function of genes located in the missing portion of the X chromosome, specifically the pseudoautosomal region. Among these genes, the SHOX gene has been most extensively studied in relation to the Turner syndrome phenotype. Haploinsufficiency of SHOX contributes to growth deficits, scoliosis, micrognathia, a high-arched palate, Madelung deformity, and reduced leg length, which are commonly observed in affected individuals. Additionally, haploinsufficiency of TIMP1 and the presence of the risk-associated phenotype of TIMP3 have been linked to a bicuspid aortic valve and aortic dysfunction. Other genes, including KDM6A, KDM5C, RPS4X, and CSF2RA, have been implicated in the phenotype but require further investigation to clarify their roles.

Karyotype-phenotype correlations reveal variations in clinical severity and comorbidity risk. Individuals with the 45,X karyotype exhibit a higher frequency of comorbidities and increased mortality, reflecting the extent of chromosome material loss. Individuals with mosaicism involving 45,X/46,XX typically present with a milder phenotype, characterized by fewer left-sided congenital heart defects, lower rates of obesity and hypertension, and a near-normal age at menarche. This group is also more likely to experience spontaneous menarche and pregnancy. Similarly, individuals with the 45,X/47,XXX karyotype tend to show milder external and cardiovascular features but face a higher risk of neurodevelopmental disabilities.

The isochromosome Xq variant generally presents an intermediate phenotype with reduced cardiac morbidity and mortality. Mosaicism of 45,X/46,XY is associated with the lowest risk of autoimmune thyroid disease and a reduced risk of coarctation of the aorta. Individuals with a ring X chromosome that retains the XIST gene face an increased risk of metabolic syndrome compared to those with 45,X karyotype. In contrast, the loss of XIST in ring X chromosome carriers is associated with a more severe cognitive phenotype.

History and Physical

Prenatal suspicion of Turner syndrome may arise from abnormal ultrasound findings, including increased nuchal translucency, cystic hygroma, left-sided cardiac anomalies (eg, coarctation of the aorta), brachycephaly, horseshoe kidney, polyhydramnios, oligohydramnios, or nonimmune fetal hydrops. Cystic hygroma results from lymphatic capillary hypoplasia and failure of the lymphatic system to communicate with the venous system in the neck, caused by haploinsufficiency of X-chromosome genes critical for normal lymphatic development. In newborns with a female phenotype, characteristic physical findings may include congenital lymphedema of the hands and feet, a webbed neck, nail dysplasia, a narrow or high-arched palate, and shortened fourth metacarpals or metatarsals.

During childhood, affected individuals commonly present with short stature and distinctive physical features, including a broad chest with widely spaced nipples, a webbed neck, a low posterior hairline, cubitus valgus, and a Madelung deformity of the forearm and wrist, characterized by ulnar and volar angulation of the distal radius with dorsal prominence of the distal ulna.[13] Although overall intelligence is typically normal, many children exhibit specific neurocognitive challenges, particularly deficits in visuospatial organization, which may manifest as learning difficulties in calculation, memory, and attention during the school years.

In adolescence, delayed puberty or primary amenorrhea is common due to premature ovarian insufficiency and is the most frequent reason for clinical evaluation, which may partly explain the mean age at diagnosis of approximately 15 years.

Cardiovascular abnormalities are a major contributor to morbidity and mortality and may be suggested by history or physical findings such as murmurs or hypertension. Common anomalies include a bicuspid aortic valve, coarctation of the aorta, an elongated transverse aortic arch, and pulmonary venous abnormalities. Progressive aortic dilation and dissection represent additional life-threatening complications. Auditory dysfunction is also common and may result from recurrent otitis media, leading to conductive hearing loss, or from defects in the cochlea's outer hair cells, causing sensorineural hearing loss.[14]

Ocular findings may include myopia, hyperopia, strabismus, amblyopia, epicanthic folds, ptosis, hypertelorism, and red–green color blindness.[15] Individuals with Turner syndrome are also at increased risk for autoimmune conditions, including autoimmune hypothyroidism, celiac disease, and inflammatory bowel disease, and may exhibit signs and symptoms of these diagnoses.[16] 

Evaluation

Diagnostic evaluation for Turner syndrome is initiated when clinical findings raise suspicion across the lifespan, from prenatal ultrasound abnormalities to characteristic physical features, growth patterns, pubertal delay, or reproductive concerns identified in childhood or adolescence. Because the phenotype is highly variable and may evolve over time, confirmation requires cytogenetic testing, with the diagnostic approach tailored to the age at presentation, clinical context, and degree of suspicion. The following sections outline prenatal and postnatal diagnostic modalities, strategies for detecting mosaicism, and recommended evaluations following confirmation of the diagnosis.

Diagnostic Modalities for Turner Syndrome

Prenatal suspicion of Turner syndrome may arise when first-trimester screening reveals findings such as low pregnancy-associated plasma protein A, increased nuchal translucency, abnormal ductus venosus flow, cystic hygroma, or hydrops. Diagnostic confirmation may be obtained through chorionic villus sampling or amniocentesis. However, the exact karyotype, particularly in cases of mosaicism, is often uncertain based solely on prenatal testing. For this reason, standard chromosome analysis using a peripheral blood sample after birth should be performed regardless of prenatal findings. A normal karyotype may occasionally be observed in cases of mosaicism. If clinical suspicion is strong, further testing or evaluation of additional metaphases is recommended.

Noninvasive prenatal testing, which analyzes cell-free fetal DNA in maternal blood, may also indicate a high risk for Turner syndrome. In such cases, nondirective genetic counseling should be provided, and invasive fetal karyotyping should be offered for confirmation. Detailed fetal ultrasonography and echocardiography are crucial for assessing structural anomalies. Preimplantation genetic testing should be considered in women planning pregnancy with their own oocytes.

Indications for testing to confirm Turner syndrome vary with the stage of life at presentation. In childhood, girls with characteristic physical features such as downslanted palpebral fissures, epicanthal folds, low-set or anomalous ears, micrognathia, narrow or high-arched palate, short neck, neck webbing, or unexplained short stature alone also warrant evaluation. Testing is further indicated when 2 or more associated features of Turner syndrome coexist, including renal anomalies (eg, horseshoe kidney, renal agenesis, hypoplasia), Madelung deformity, neuropsychological or psychiatric difficulties, multiple typical nevi, dysplastic or hyperconvex nails, congenital heart defects, or early-onset sensorineural hearing loss (before age 40) in the presence of short stature.

Karyotype analysis using peripheral blood mononuclear cells is the gold standard and considered the first diagnostic step. A minimum of 30 metaphases should be analyzed to detect mosaicism at approximately 10% with 95% confidence limits.[17] Other molecular genetic techniques, including microarray, exome sequencing, and genome sequencing, may also be used. However, microarray analysis may be less effective than sequencing methods at detecting low-level mosaicism.

When karyotype results are normal in a patient with clinical features suggestive of Turner syndrome, a second analysis using a different tissue source, such as skin fibroblasts, buccal mucosa cells, or bladder epithelial cells, should be considered. In individuals with a 45,X karyotype who present with signs of virilization, molecular studies should be performed to detect Y-chromosome material, which may be identified by karyotyping, fluorescence in situ hybridization with Y-chromosome probes, polymerase chain reaction using Y-specific primers, or array comparative genomic hybridization. Approximately 10% to 12% of affected individuals may carry a normal or structurally abnormal Y chromosome.

During adolescence, patients may present with delayed puberty or primary amenorrhea. Elevated serum follicle-stimulating hormone levels support the diagnosis of Turner syndrome, whereas anti-Müllerian hormone may serve as a more sensitive marker for predicting ovarian insufficiency.[18] Once Turner syndrome is diagnosed, a comprehensive evaluation should be conducted to identify associated abnormalities, including cardiac and renal anomalies and neurocognitive impairments. Baseline screening should be performed at diagnosis, followed by periodic assessments throughout life. (see Table 2).

Table

Table 2. Evaluation of Turner Syndrome Comorbidities by Developmental Stage and Organ System.

ALP, alkaline phosphatase; ALT, alanine aminotransferase; AMH, anti-müllerian hormone; AST, aspartate aminotransferase; BMI, body mass index; CBC, complete blood count; DXA, dual-energy x-ray absorptiometry; GGT, γ-glutamyl transferase; HbA1c, hemoglobin a1c; TSH, thyroid stimulating hormone; TTE, transthoracic echocardiogram; UTI, urinary tract infection

Cardiac Evaluation

Fetal 2-dimensional echocardiography should be performed when Turner syndrome is diagnosed prenatally. Conversely, the presence of a left-sided cardiac lesion, excluding a bicuspid aortic valve, in a female fetus should prompt evaluation for Turner syndrome. All infants or children diagnosed with Turner syndrome should undergo a transthoracic echocardiogram (TTE) on the second or third day of life or at the time of diagnosis, even in the absence of clinical signs. TTE should assess for a bicuspid aortic valve, coarctation of the aorta, partial anomalous pulmonary venous return, hypoplastic left heart syndrome, and coronary artery anomalies, including visualization of their origin and proximal course.

Cardiac magnetic resonance imaging (MRI) provides superior visualization of extracardiac vascular anomalies compared with TTE and should be included in the initial evaluation of all children and adults. In children with adequate TTE visualization and no abnormalities, cardiac MRI or computed tomography (CT) may be deferred until imaging can be performed without anesthesia. Electrocardiography (ECG) should be performed at the initial evaluation to assess for rhythm abnormalities.

If the initial cardiac evaluation is normal, follow-up should be performed in individuals aged 9 to 11 and should include an ECG, blood pressure measurement, and a TTE. In the absence of aortic dilation, the next examination may be performed upon completion of growth, incorporating ECG, blood pressure, and cardiac MRI or CT to establish baseline aortic imaging. Cardiac assessment is recommended again during the transition to adult care, with counseling on future surveillance, lipid monitoring, and pregnancy planning. Cardiac evaluations should continue every 5 to 10 years in asymptomatic adults with Turner syndrome.

Cardiology consultation is advised during pregnancy or fertility counseling, upon the onset of new cardiovascular symptoms, or after the diagnosis of a cardiac condition, such as a bicuspid aortic valve or aortic dilation. Lifelong monitoring is essential because of the substantially increased risk of aortic dilation and dissection—164 per 100,000 person-years compared with 6 per 100,000 person-years in the general population. Turner syndrome-specific aortic Z-scores should be applied for patients younger than 15 years. For individuals older than 15 years, assessment may use the aortic height index, aortic size index, Turner syndrome-specific Z-scores, or general population Z-scores, depending on local protocols.[19]

Neuropsychological Evaluation and Counseling

Neuropsychological evaluation and counseling should begin at diagnosis and continue throughout development. These services address anticipatory guidance, developmental surveillance, social cognition, learning and educational challenges, psychosexual concerns, and reproductive health.

Treatment / Management

Short Stature

Short stature is frequently the initial presenting concern in girls with Turner syndrome. Results from large studies have reported an untreated adult height deficit of approximately 20 cm (8 inches) compared to the general population, equivalent to a 3-standard-deviation reduction. The median untreated adult height is approximately 143-144 cm (4 feet 8 inches).[20] Although growth hormone deficiency is not a characteristic feature of Turner syndrome, affected individuals often respond favorably to human growth hormone (hGH) therapy. Initiation of hGH therapy is recommended as early as age 2 in individuals who exhibit growth decline, short stature, or a high likelihood of developing short stature. Early initiation is especially beneficial because growth velocity diminishes rapidly during early childhood, particularly within the first 2 years. Greater height gains are achieved during the prepubertal years when treatment begins early.[21]

Response to hGH varies among patients. However, an average annual height gain of 1 cm has been observed during therapy. The initial dosage of hGH is substantially higher than that used for growth hormone deficiency, typically 40 to 50 mcg/kg/day. It may be increased to 68 mcg/kg/day in cases of suboptimal response. Please see StatPearls' companion resource, "Short Stature," for further information. Therapy with hCG should be continued until a bone age of approximately 14 years is reached or height velocity declines to less than 2 cm/year. Treatment may be discontinued earlier if the patient is satisfied with the attained height. Growth hormone therapy may occasionally unmask preexisting scoliosis; therefore, regular monitoring of spinal alignment is essential throughout treatment. Development of scoliosis warrants referral to an orthopedic surgeon for evaluation and consideration of bracing or surgical correction. Other potential adverse effects, consistent with those observed in other contexts of hGH use, include intracranial hypertension, slipped capital femoral epiphysis, and local injection-site reactions.

When hGH alone does not produce an adequate increase in height velocity, additional growth-promoting measures, such as low-dose oxandrolone (30-50 mcg/kg/day) or postponement of pubertal induction, may be considered. The recent withdrawal of oxandrolone's approval by the United States Food and Drug Administration (FDA) due to safety concerns warrants careful consideration in clinical decision-making. Regional regulatory status and clinical guidelines should inform the use of this agent.[Source: FDA, 2023]

Therapy with hCG is generally considered safe. However, evidence regarding the effect of this agent on aortic diameter is conflicting. A cautious approach is warranted in individuals with cardiovascular risk factors, particularly aortic dilation. Serum insulin-like growth factor 1 should be measured at least annually, with values maintained within the reference range (±2 standard deviations). Preliminary data support the safety and efficacy of long-acting growth hormone in children with Turner syndrome, although additional studies are needed before this agent can be adopted as a standard therapeutic option.

Individuals with Turner syndrome have a higher baseline risk of metabolic complications than the general population, and hGH therapy may further increase this risk. Long-term follow-up studies are needed to determine the optimal timing and frequency of metabolic monitoring for patients receiving hGH treatment.

Cardiac Health

Both congenital and acquired cardiac conditions are common in Turner syndrome and are a leading cause of morbidity and mortality in adulthood. Congenital heart disease is present in approximately 50% of affected children and may include a bicuspid aortic valve, coarctation of the aorta, hypoplastic left heart syndrome, or aortic arteriopathy. Over a lifetime, nearly 25% of individuals develop an aortic aneurysm. Cardiac management in individuals with Turner syndrome and congenital heart disease should follow established standards of care for other patients with congenital heart disease across the lifespan. Similarly, valvular diseases should be treated according to standard guidelines, with additional counseling regarding the increased cardiovascular risks associated with Turner syndrome.

In adults, aortic dilation carries a significant risk of aortic dissection and warrants active surveillance. Elective aortic surgery should be considered in the presence of moderate dilation, defined as an aortic height index >23 mm/m, an aortic size index >2.3 cm/m², or a Z-score >3.5, when at least 1 risk factor is present, such as a bicuspid aortic valve, coarctation of the aorta, hypertension, or a rapid increase in diameter (>3 mm/year). Severe dilation (aortic height index >25 mm/m, aortic size index >2.5 cm/m², or Z-score >4) also warrants surgical evaluation. Z-scores should guide clinical decision-making in children younger than 15.

A prolonged QT interval requires avoiding QT-prolonging medications, including antiarrhythmics, macrolides, fluoroquinolones, and certain psychiatric drugs. Coarctation of the aorta, when present, requires surgical correction. Antihypertensive therapy with β-blockers, angiotensin receptor blockers, or both is recommended in patients with aortic dilation or an aortic Z-score over 2.5, even in the absence of hypertension.[23] For individuals with normal aortic dimensions, blood pressure management should follow the general guidelines for pediatric or adult hypertension. Patients with aortic dilation should limit exercise intensity to reduce cardiovascular risk.

Preconception and prenatal cardiac care should include cardiac MRI to assess aortic dimensions and aortic valve anatomy. If baseline findings are normal, at least 1 TTE assessment should be performed during pregnancy. Comprehensive cardiac risk assessment is essential before conception, with a clearly defined management plan outlining follow-up intervals and the mode of delivery. Pregnancy care should be coordinated at centers experienced in managing Turner syndrome during pregnancy.

Ovarian Failure

Girls with Turner syndrome commonly present with primary amenorrhea or delayed puberty due to premature ovarian failure. To facilitate diagnosis and timely referral for fertility preservation, serum follicle-stimulating hormone (FSH), luteinizing hormone, and anti-Müllerian hormone (AMH) levels should be measured at ages 8 to 9 years and monitored annually until ages 11 to 12 years. The reference range for AMH in healthy girls ages 6-19 is 0.98-7.84 ng/mL (7–56 pmol/L).[22] Serum AMH is a useful marker of ovarian function. Detectable AMH levels are associated with a higher likelihood of spontaneous pubertal onset, whereas levels below 0.56 ng/mL (4 pmol/L) are strongly associated with absent pubertal development. Estrogen replacement should be initiated if breast development has not begun by 11 to 12 years of age.   

Approximately one-third of individuals with a 45,X karyotype experience spontaneous pubertal development, which occurs more often in those with mosaicism. Nevertheless, spontaneous menarche and successful pregnancy remain uncommon. Therefore, hormone replacement therapy is required in most cases to induce and maintain secondary sexual characteristics and support long-term reproductive health.

Hormone replacement therapy

The guiding principle of estrogen therapy in Turner syndrome is to replicate normal physiology as closely as possible in terms of timing, duration, and progression. Therapy is generally initiated between the ages of 11 and 12, after confirmation of elevated FSH on at least 2 separate occasions. Low-dose estrogen may be introduced alongside hGH therapy for girls diagnosed later. The preferred estrogen for replacement is 17β-estradiol, which is identical to the body's endogenous estrogen. The transdermal route is considered the most physiological and preferred whenever feasible. Oral estradiol is an effective alternative and superior to other synthetic estrogen preparations.

Initial estrogen therapy should begin at a low dose to mimic the gradual hormonal rise of early puberty. A typical starting regimen includes 7 mcg of transdermal estradiol or 0.25 mg of the oral form, equivalent to approximately one-eighth of an adult replacement dose. The dose is increased every 6 to 12 months, aiming to reach adult levels by the fourth year of treatment. This titration may be implemented by initially using one-fourth of a 25 mcg estradiol patch or a 1 mg estradiol valerate tablet, then increasing to half and then to a full patch or tablet in the second and third years, respectively. By the fourth year, full adult dosing—typically 50 mcg (up to 200 mcg) transdermally or 2 mg (up to 4 mg) orally—should be achieved.

Estrogen titration should be guided by clinical and laboratory markers, including breast development and serum estradiol concentrations, with a target of 100 to 150 pg/mL at full replacement. Additional indicators, such as uterine maturation assessed by pelvic ultrasound and bone mineral density measured by dual-energy x-ray absorptiometry, can aid in evaluating treatment adequacy. Patients who enter puberty spontaneously but subsequently develop gonadal failure should receive estrogen doses corresponding to their Tanner stage, as they often require higher initial levels than those used in prepubertal individuals. 

Progesterone therapy

Cyclic progesterone should be initiated after 18 to 24 months of estradiol therapy, once withdrawal bleeding begins. This intervention induces and maintains regular uterine bleeding and prevents endometrial hyperplasia. If bleeding occurs earlier in the replacement course, transabdominal or transvaginal ultrasound should be used to guide therapy, with a target endometrial thickness of 4 to 8 mm. Estradiol doses should be increased to promote further maturation of the endometrium and secondary sexual characteristics if the endometrium remains below this threshold or if Tanner stage 3 breast development has not been achieved. Micronized progesterone at 200 mg daily for 12 days a month is the preferred regimen. Dydrogesterone 10 mg daily for 12 days is an acceptable alternative.

Hormone replacement therapy in adults with Turner syndrome

Hormone replacement therapy should be maintained into adulthood with a cyclic combination of estrogen and progesterone, typically continued until the average age of menopause, approximately 50 years. Beyond this age, the need for ongoing therapy should be reassessed, with consideration of lower-dose regimens tailored to individual clinical circumstances. In adult women, treatment may be individualized based on preference and tolerability to enhance adherence. Combined formulations are often preferred because they differ from the sequential regimens typically used during adolescence. In addition to facilitating pubertal development and maintaining menstrual function, hormone replacement therapy confers several systemic benefits. Reported advantages include reduced requirements for antihypertensive, antidiabetic, and thyroid medications, as well as lower rates of hospitalization for cerebrovascular disease and osteoporotic fractures.[23]

Fertility considerations

Approximately 10% of individuals with Turner syndrome can achieve spontaneous pregnancy. In many patients, the ovaries are replaced by fibrous tissue ("streak gonads") containing few or no functional follicles. Predictors of fertility include spontaneous menarche, mosaic karyotypes with partial preservation of the second X chromosome, detectable serum AMH levels, and FSH concentrations below 10 IU/L. However, pregnancies in this population are frequently complicated by significant maternal and fetal risks, including a 3-fold increase in miscarriage rates, a higher incidence of preeclampsia, elevated cesarean delivery rates, increased rates of small-for-gestational-age neonates, preterm birth, and fetal anomalies.

Fertility preservation strategies may be considered for individuals unable to conceive spontaneously. Controlled ovarian stimulation followed by oocyte cryopreservation may be offered after menarche, with appropriate psychological counseling beforehand. Ovarian tissue cryopreservation is investigational and should be performed only within ethically approved research protocols. Oocyte or embryo donation and the use of gestational carriers are viable alternatives for patients unable to achieve pregnancy with their own gametes, particularly given the considerable cardiovascular and obstetric risks associated with pregnancy in this group. All fertility-related counseling, treatment, and follow-up should be conducted in specialized centers. These facilities should be staffed by an interprofessional team that includes endocrinologists, cardiologists, reproductive specialists, and clinicians experienced in the coordinated management of Turner syndrome.[24]

Gonadoblastoma and Other Cancers

Patients with marker chromosome elements on karyotyping or evidence of virilization should be evaluated for the presence of Y chromosome material. The presence of Y chromosome sequences confers an increased risk of gonadoblastoma. Reported incidence rates vary widely (0% to 100%), whereas the risk of malignant transformation is relatively low (1% to 22%). Gonadoblastoma most often develops after the second decade of life and rarely metastasizes. Owing to the lack of reliable clinical or imaging markers for surveillance and the potential for loss to follow-up, decisions regarding prophylactic gonadectomy should be individualized, carefully weighing the associated risks and benefits. Routine cancer surveillance beyond standard population guidelines is not currently recommended for this group. However, evidence from recent studies suggests a higher incidence of colon cancer than in the general population, underscoring the need for further large-scale, long-term research to refine screening recommendations.[25] 

Bone Health

Low bone mineral density and increased fracture risk are common in individuals with Turner syndrome. Estrogen replacement, along with adequate vitamin D and calcium supplementation, can mitigate these risks.[26] Turner syndrome is also associated with an increased prevalence of scoliosis, warranting annual screening during height growth years. (see the Complications section for more details).

Neuropsychiatric Function

Despite normal intelligence, girls with Turner syndrome frequently experience learning disabilities that may require specialized education and assessment. Interventions should be tailored to the diagnosed disability. Although earlier reports suggested a higher prevalence of psychiatric illnesses, including depression, a recent nationwide retrospective study from Sweden found a lower prevalence of psychiatric conditions in individuals with Turner syndrome than in the general population. This finding urges caution against overdiagnosing severe psychiatric disorders in this group.[27]

Hearing Loss

Early tympanostomy intervention is recommended for middle ear disease, following protocols similar to those used for other high-risk populations. Evaluation methods and frequencies across life stages are outlined in Table 2.

Renal Conditions

Renal abnormalities are common in Turner syndrome, including collecting system malformations, positional or horseshoe kidneys, and malrotation. Obstruction caused by ureteropelvic junction anomalies may lead to hydronephrosis and increase the risk of pyelonephritis.[28] Patients with detected abnormalities should be promptly referred to nephrology and urology specialists, as appropriate. 

Transition Care

The transition from adolescence to adulthood, typically occurring between ages 14 and 25, is a critical period in the care of individuals with Turner syndrome and is often associated with decreased adherence to follow-up. Historically, the transfer from pediatric to adult services has been a period when many patients are lost to care, underscoring the importance of emphasizing lifelong follow-up to ensure continuity and holistic management. Expert recommendations highlight the use of structured tools to assess readiness for transition, evaluate the adolescent's autonomy and understanding of their condition, address evolving issues such as fertility and psychological health, and facilitate early introduction to adult care clinicians. Although gradual, well-supported transitions are ideal and associated with improved outcomes, successful implementation remains dependent on available resources and personnel.[29]

Differential Diagnosis

The clinical features of Turner syndrome overlap with those of several genetic and developmental disorders, and different conditions can mimic the phenotype at various stages of life. Awareness of age-specific diagnostic considerations is essential for accurate identification and management.

Prenatally, findings such as cystic hygroma, nonimmune fetal hydrops, coarctation of the aorta, and increased nuchal translucency may raise suspicion for Turner syndrome, but are not pathognomonic. Similar ultrasound abnormalities may also be seen in trisomy 21, trisomy 18, and Noonan syndrome, which should be considered in the differential diagnosis.[30]

In infancy and childhood, short stature accompanied by characteristic morphologic features resembling Turner syndrome can occur in conditions such as Noonan syndrome and SHOX haploinsufficiency. Noonan syndrome, in particular, shares overlapping features with Turner syndrome, including webbed neck, short stature, and congenital cardiac or renal anomalies; however, it affects both boys and girls, whereas Turner syndrome occurs exclusively in girls.

During adolescence, delayed or absent pubertal development may reflect alternative etiologies, including 46,XX gonadal dysgenesis, 46,XY complete gonadal dysgenesis, or premature ovarian insufficiency related to other genetic abnormalities, such as deletions distal to Xq24.

Because multiple conditions can present with features similar to Turner syndrome at different developmental stages, targeted genetic and endocrine evaluation is critical to establish the correct diagnosis and guide appropriate treatment, surveillance, and counseling.

Prognosis

The prognosis for Turner syndrome has improved substantially with advances in multidisciplinary care, including growth hormone therapy, hormone replacement therapy, structured cardiovascular surveillance, fertility counseling, psychosocial support, and proactive management of comorbidities. Although gaps remain in understanding the genetic mechanisms of specific complications and in optimizing individualized treatment strategies, contemporary care has markedly improved functional outcomes and quality of life for many affected individuals. (see Evaluation and Treatment/Management sections for details)

Despite these improvements, overall mortality remains higher than in the general population. Large population-based studies report approximately a threefold higher mortality rate among individuals with Turner syndrome, with excess risk observed across all karyotypes and greatest among those with a 45,X or isochromosome Xq karyotype. Median survival is reduced, with estimates of approximately 69 years overall and somewhat lower survival among individuals with a 45,X karyotype.[31] In long-term follow-up cohorts, survival rates are significantly lower than in age-matched controls, with cardiovascular disease accounting for the majority of premature deaths.

Cardiovascular disease is the leading determinant of prognosis, accounting for up to half of all deaths in Turner syndrome. Aortic aneurysm, dissection, and rupture—often occurring in young adulthood—are the most serious and potentially fatal complications. Coronary heart disease and stroke become increasingly important contributors to mortality with advancing age. Other causes of excess mortality include liver disease, malignancy, pneumonia, diabetes mellitus, epilepsy, and renal disease.[32]

Prognosis is influenced by karyotype, the presence and severity of congenital heart disease (particularly left-sided obstructive lesions), and the timing of diagnosis. Earlier recognition enables the timely initiation of growth hormone and estrogen replacement therapies and the implementation of surveillance strategies that reduce morbidity and improve long-term outcomes.[33] With appropriate lifelong monitoring and intervention,  individuals with Turner syndrome can lead productive, independent lives, although ongoing medical follow-up remains essential.

Complications

Turner syndrome is associated with increased morbidity across the lifespan due to multisystem comorbidities affecting cardiovascular, endocrine, skeletal, metabolic, reproductive, auditory, and neurocognitive domains. These complications contribute substantially to disease burden and underlie the increased mortality observed in affected individuals.

Common complications and comorbidities include:

• Growth and reproductive complications: short stature, delayed or absent puberty, premature ovarian insufficiency, and infertility
• Cardiovascular disease: congenital heart defects (including bicuspid aortic valve and coarctation of the aorta), progressive aortic dilation, aortic aneurysm and dissection, coronary artery disease, hypertension, and stroke
• Skeletal and metabolic bone disease: osteoporosis, osteopenia, scoliosis, and other skeletal abnormalities
• Auditory dysfunction: recurrent otitis media with conductive hearing loss and sensorineural hearing loss
• Autoimmune disease: autoimmune hypothyroidism, celiac disease, and other autoimmune conditions
• Renal and hepatic abnormalities: congenital renal malformations and liver function abnormalities, including metabolic dysfunction–associated steatohepatitis.
• Neurocognitive and psychosocial challenges: deficits in visuospatial and executive functioning, and learning disabilities
• Metabolic disorders: central obesity, insulin resistance, type 1 or type 2 diabetes mellitus, and dyslipidemia
• Oncologic risk: increased risk of gonadoblastoma in individuals with Y chromosome material

Additional complications may arise secondary to treatment, including adverse effects related to growth hormone therapy or hormone replacement, underscoring the need for individualized risk–benefit assessment and careful monitoring.

Together, these complications necessitate coordinated, lifelong surveillance and management to mitigate morbidity, prevent life-threatening outcomes, and optimize long-term health and quality of life.

Consultations

Comprehensive care for individuals with Turner syndrome requires the timely involvement of multiple specialists to monitor and treat its diverse manifestations. Coordinated consultations with the following specialties help ensure optimal outcomes across developmental stages:

• Pediatric or adult endocrinology for hormone management and growth monitoring
• Pediatric or adult cardiology for congenital and acquired cardiac evaluation and surveillance
• Medical genetics for diagnosis, counseling, and genetic risk assessment
• Gynecology and fertility specialists for reproductive health and fertility preservation
• Audiology for hearing assessment and management of middle and inner ear disorders
• Ophthalmology for vision screening and evaluation of ocular abnormalities
• Orthopedic surgery for evaluation and treatment of musculoskeletal issues, such as scoliosis
• Nephrology and urology for the management of renal malformations and urinary tract abnormalities
• Ongoing communication between specialties enhances care quality and addresses evolving needs over time. Such interprofessional collaboration is crucial throughout the patient's life.

Deterrence and Patient Education

Early recognition of Turner syndrome and consistent patient and family education are essential to reducing diagnostic delay, preventing avoidable complications, and improving long-term outcomes. Education should be tailored to the stage of life at the time of presentation and directed to families, patients, and clinicians involved in ongoing care.

Prenatal Diagnosis 

When Turner syndrome is diagnosed in a fetus, counseling should be nondirective and include discussion of all reproductive options, including continuation or termination of the pregnancy, as well as the broad phenotypic spectrum of Turner syndrome, potential medical needs, long-term prognosis, and available supports. Counseling should acknowledge uncertainty about individual outcomes and allow families time to process the diagnosis. Ongoing access to clinicians experienced in the lifelong management of Turner syndrome can help families make informed decisions and prepare for postnatal care if the pregnancy is continued.

Neonatal Diagnosis and Early Education

In the neonatal period, Turner syndrome may present with characteristic features such as congenital lymphedema of the hands and feet, webbed neck, low posterior hairline, cardiac murmurs, or renal anomalies. Early diagnosis allows prompt evaluation for congenital heart and kidney disease and establishes a framework for long-term surveillance. Families should receive clear, compassionate education about the diagnosis, expected clinical course, and the importance of regular follow-up, emphasizing the wide variability in outcomes and the potential for a good quality of life with appropriate care.

Childhood Diagnosis and Ongoing Education

During childhood, short stature is often the most prominent feature prompting evaluation. Additional findings, such as recurrent otitis media with hearing loss or learning challenges, may also raise suspicion. Education at this stage should focus on the rationale for growth hormone therapy, routine monitoring for comorbidities, and the importance of developmental and educational support. Empowering families to recognize evolving health needs and maintain consistent follow-up helps reduce missed opportunities for intervention.

Adolescent Diagnosis and Transition-Focused Education

In adolescence, delayed puberty or primary amenorrhea often prompts diagnosis. Education should address pubertal induction, fertility implications, psychosocial well-being, and the importance of ongoing medical surveillance. Adolescents should be progressively engaged in understanding their condition, encouraged to develop autonomy in health management, and supported through discussions of reproductive options and long-term health risks. This stage offers a critical opportunity to reinforce lifelong adherence to care and prepare for transition to adult services.

Pregnancy in Individuals With Turner Syndrome

Preimplantation genetic testing may be offered to individuals with Turner syndrome who pursue pregnancy using their own oocytes. Those with mosaic karyotypes (45,X/46,XX) who conceive spontaneously should be offered prenatal diagnostic testing. Education should emphasize the high-risk nature of pregnancy in Turner syndrome, particularly cardiovascular risks, and the need for multidisciplinary care involving cardiology, maternal–fetal medicine, and endocrinology.

Role of Clinician Education and Public Awareness

Despite recognizable clinical features, the median age at diagnosis remains approximately 15 years, reflecting persistent gaps in early recognition. Improving awareness among primary care physicians, pediatric clinicians, and the public regarding the clinical features of Turner syndrome and indications for karyotype testing is essential to facilitate earlier diagnosis, timely intervention, and improved long-term outcomes.

Enhancing Healthcare Team Outcomes

Individuals with Turner syndrome require lifelong, multidisciplinary care to monitor and manage the diverse medical, developmental, and psychosocial challenges of their condition. While primary care clinicians typically oversee ongoing surveillance and general health maintenance, optimal management depends on a coordinated interprofessional team. Core medical specialties commonly involved include cardiology, endocrinology, gynecology and reproductive medicine, nephrology, ophthalmology, audiology, orthopedics, and psychology or neurodevelopmental services.

Nonphysician team members are essential to comprehensive care. Genetic counselors and specialized nurses provide patient and family education, facilitate referrals, and support communication across disciplines. Pharmacists assist with medication management, including hormone replacement therapy, and help ensure adherence and safe administration. Registered dietitians and physical or occupational therapists may also play critical roles in addressing growth, obesity prevention, bone health, and functional development.

Clear communication among team members, coordinated by the primary care physician, ensures timely identification and management of complications, supports patient-centered decision-making, and enhances continuity of care. An interprofessional approach is vital for optimizing long-term outcomes and quality of life in girls and women with Turner syndrome.

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Disclosure: Lokesh Sharma declares no relevant financial relationships with ineligible companies.

Disclosure: Sharon Daley declares no relevant financial relationships with ineligible companies.