Characterization of pulsatile secretion of gonadotropin and prolactin in women with normal menstrual cycle, secondary amenorrhea and polycystic ovary syndrome (PCOS).

To characterize the episodic fluctuations of serum LH, FSH and PRL in women with normally cycling, secondary amenorrhea and polycystic ovary syndrome (PCOS), four groups of women were studied: group I (N = 8) consisted of normal women in the follicular phase of the cycle; group II (N = 10) of women with secondary amenorrhea and positive progesterone withdrawal bleeding; group III (N = 8) of women with secondary amenorrhea and negative progesterone withdrawal bleeding; group IV (N = 9), women with polycystic ovary syndrome (PCOS). Blood samples were obtained at 15 minute intervals for 4 hours during one admission day. Ovarian steroids were measured to evaluate the baseline endocrine environment in each group. Distinct pulsatile fluctuations of serum LH, FSH and PRL were observed in all subjects. These pulses showed a high degree of coincidence in LH with FSH and LH with PRL in each group. However, the mean (+/- SD) frequencies of LH in group III and group IV were significantly lower (P < 0.01) and higher (P < 0.01) than in group I, respectively. The mean frequencies of FSH in groups III and IV were lower (P < 0.05), as compared with those of group I. The mean amplitude of LH in group IV was significantly higher (P < 0.001) than in group I. These results suggest that loss of the regulatory pulsatility of gonadotropin releases may be a contributory cause to anovulation and secondary amenorrhea. The concomitant pulsatile releases of gonadotropin and PRL are essential to reproductive function and their regulatory controls in the follicular phase may be mediated through a common neuroendocrine mechanism in normal and hypogonadal women.