Background: Acquired subclinical hypothyroidism in adulthood is mainly due to autoimmune thyroiditis. In the absence of a goiter or a palpable firm thyroid, measurement of thyroid antibodies can improve the diagnosis. Whether thyroid antibodies are detected or not, what might be the clinical relevance of ultrasonography in this setting?
Methods: We studied 1845 cases of subclinical hypothyroidism in adults recruited for symptoms indicative of hypothyroidism or thyroid pathology. All patients were screened for thyroid antibodies and underwent an ultrasonographic thyroid examination. LOCALISATION: Multicentric retrospective study.
Results: Chronic autoimmune thyroiditis was confirmed in 70% of patients. Thyroid antibodies were undetectable in 30% of patients. In all patients, thyroid ultrasound facilitated measurement of the thyroid volume and detection of non-palpable nodules and therefore allowed biopsy. In patients negative for thyroid antibodies, ultrasonography suggested autoimmune thyroiditis in 31% of cases. Ultrasonography did not contribute to diagnosis in a large number of patients without nodules and in case of normal echostructure. The strategy of thyroid hormone replacement therapy was not influenced by ultrasonographic data. Thyroid biopsies detected smears suspected to be cancerous in 10 patients (4%). Cancer was confirmed in nine patients after surgery. Ultrasonography displayed suspicious aspects in six patients.
Conclusion: In subclinical hypothyroidism, thyroid ultrasonography is not required for the diagnosis of autoimmune thyroiditis but is useful for patients with abnormal thyroid palpation and allows detection of non-palpable thyroid nodules. For patients that were negative for thyroid antibodies, thyroid ultrasonography can improve diagnosis for some patients, allowing detection of autoimmune thyroiditis.