Send to

Choose Destination
Gynecol Obstet Invest. 1995;39(3):197-200.

Serum levels of relaxin during the menstrual cycle and oral contraceptive use.

Author information

Department of Clinical Neuroscience and Family Medicine, Karolinska Institute, Huddinge, Sweden.


Serum relaxin levels were analysed in 12 healthy women every other day during the menstrual cycle and during a second cycle on oral contraceptives. Relaxin levels in 7 women with posterior pelvic and lumbar pain were also measured. Relaxin was detected during both the follicular and luteal phases of the menstrual cycle in some of the healthy women. Serum levels were further increased during the use of oral contraceptives. Oestradiol levels in the untreated women correlated to the relaxin levels. Women with posterior pelvic and lumbar pain had higher relaxin levels than did healthy women, a finding that needs to be further explored. Our data indicate the existence of sources for relaxin production other than the corpus luteum in the non-pregnant woman. Endogenous and exogenous oestrogens may stimulate the production of relaxin.


In Sweden, clinicians took blood samples every other day during one menstrual cycle from 12 healthy women aged 19-42 taking no medication and during a second menstrual cycle from 9 of these women while using a combined oral contraceptive (OC) (150 mcg desogestrel + 30 mcg ethinyl estradiol). They also took samples from a second group of 7 women, 26-42 years old, with a long history of posterior pelvic pains and symptoms in the lower lumbar region during 2 consecutive menstrual cycles. The 7 women did not use OCs but did take paracetamol. The researchers aimed to measure the serum relaxin levels in all the women to determine whether OCs inhibit relaxin secretion and to determine whether changes in relaxin secretion causes posterior pelvic pain. 7 of the 12 healthy women had detectable levels of relaxin during either the follicular or luteal phases or both phases of the menstrual cycle. Relaxin secreted during both phases suggests that the corpus luteum is not the only source of relaxin in nonpregnant women, as commonly believed. As estradiol levels increased so did the relaxin levels (r = 0.44; p 0.05). During OC use, 6 of the 9 women had detectable levels of relaxin. The mean relaxin levels were higher during OC use than during the non-OC cycle (range, 20-255 vs. 20-135 ng/l), except during days 26-32. In fact, the number of relaxin measurements above the detection limit (20 ng/l) during OC use (i.e., anovulation) was much higher than during the normal ovulatory cycle (40 vs. 20; p 0.001). It appears that relaxin secretion does not depend on ovulation. The positive correlation between estradiol and relaxin levels and the increased relaxin levels during OC use suggests that estradiol and ethinyl estradiol regulate relaxin synthesis. All 7 women with posterior pelvic pain had detectable serum relaxin levels. They had detectable relaxin levels significantly more often than did healthy women (p 0.001). Further research is needed to understand the pathophysiological role of relaxin in lower back pain.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for S. Karger AG, Basel, Switzerland
Loading ...
Support Center