Circadian variation in concentration of anti-Müllerian hormone in regularly menstruating females: relation to age, gonadotrophin and sex steroid levels.

BACKGROUND Anti-Müllerian hormone (AMH) is a promising marker of ovarian reserve. The aim of the study is to assess the circadian variation in AMH, and to evaluate its clinical relevance and biological aspects as an effect of age and other endocrine mechanisms involved in the regulation of AMH secretion. METHODS Nineteen healthy non-smoking, regularly menstruating female volunteers with body mass index below 30 kg/m(2), 10 aged 20-30 years (Group A) and 9 aged 35-45 (Group B) were included. Blood sampling, initiated at 8:00 a.m. on Days 2-6 of the menstrual cycle, was continued every second hour until 8:00 a.m. the following day. Serum levels of AMH, FSH, LH, progesterone and estradiol were measured. RESULTS With 8:00 a.m. values at the first day of investigation as a reference, the mean concentrations in the pooled data revealed a significantly lower level at 4:00 a.m. (P = 0.021) and 6:00 a.m. (P = 0.005) with a maximum mean difference of 1.9 pmol/l (10.6%). The same pattern was seen in both the age groups. Including both the age groups, the overall circadian variation of the AMH levels did not reach statistical significance (P = 0.059). A significant positive correlation between AMH and LH concentration was seen over the 24-h period (P < 0.001). CONCLUSIONS A slight decrease in serum AMH levels during the late night appears not clinically relevant. Co-variation in the levels of LH and AMH might indicate joint regulatory mechanisms for the latter hormone and gonadotrophins.