RESUMO
BACKGROUND: Anti-mullerian hormone (AMH) is a marker of ovarian function and reserve and reflects the number and size of antral follicles. The objective of this study was to evaluate the effect of FSH suppression on AMH levels, during the late luteal phase of human menstrual cycle, with the use of oral contraceptives pills (OCP). METHODS: Twenty normovulatory infertile women were included in the study. On the third day of a spontaneous menstrual cycle, the patients were submitted to a transvaginal ultrasound examination and blood sample collection. From the 20th day of this menstrual cycle, the patients took daily OCP, containing 0.030 mg of ethinyl-estradiol plus 0.15 mg of desogestrel. On the third day of the following cycle, the measurements were repeated. RESULTS: After OCP use, the levels of FSH and estradiol were significantly reduced (P < 0.001). The number of antral follicles measured on both occasions did not differ, although after OCP use, the follicles presented significantly lower diameters (mean 4.4 + 1.7 mm before OCP versus 3.5 + 1.2 mm after OCP P < 0.001). The levels of AMH were significantly reduced after pituitary suppression, with a median (inter-quartile range) of 3.02 ng/mL (1.21-6.39) before OCP and 2.22 ng/mL (0.9-3.11) after OCP, P = 0.04. CONCLUSIONS: The short administration of OCP in late luteal phase caused suppression of FSH secretion during the cycle transition, leading to a more homogeneous follicular cohort. The lower AMH levels observed, although simultaneous with FSH suppression, were probably not a direct effect of the reduced FSH levels, but were more likely a consequence of the lower production by the arrested follicular cohort.