Effects of bromocriptine on endocrine environment in the polycystic ovary syndrome

In order to investigate the hormone feature and the effect of bromocriptine on endocrine profile in patients with polycystic ovary syndrome (PCO), twenty-four-hour secretion pattern of LH, FSH, PRL and testosterone were assessed in 8 PCO patients and 4 normal women as controls by obtaining serial blood samples, taken through a forearm cannula, at 30 minute intervals for 24 hours. Bromocriptine, 5 mg/day was given and 3 patients were reassessed in the follicular phase of the menstrual cycle after ovulatory periods were established during bromocriptine therapy. There was significant difference in pulse amplitude, but not in pulse frequency of LH and testosterone between PCO and normal women (23.1 +/- 9.49 vs 5.75 +/- 1.28 mIU/ml, p less than 0.01; 27.8 +/- 10.1 vs 10.2 +/- 2.63 ng/dl, p less than 0.01), and the 24 hour mean LH and testosterone levels were higher (p less than 0.01) in PCO (52.3 +/- 20.1 mIU/ml, 105.1 +/- 15.9 ng/dl) than in normal women (13.4 +/- 4.31 mIU/ml, 54.3 +/- 13.3 ng/dl). Though a pulsatility in FSH secretion was identified, no difference between normal women and PCO was observed. Mean PRL level was within the normal range in PCO but with a higher pulse frequency (p less than 0.01) and lower pulse amplitude (p less than 0.01) than those of the normal women. Furthermore, LH and testosterone secretions maintained the circadian changes in PCO patients against the normal women. During bromocriptine therapy, mean level and pulse amplitude of LH and testosterone were significantly suppressed, without changing in pulse frequency, whilst PRL secretory patterns were not reestablished. In conclusion we have found that PCO is associated with high level and pulse amplitude of LH and testosterone, with high frequency and low amplitude of PRL, and bromocriptine administration can blunt LH, PRL and testosterone secretion, suggesting a hypothalamic intervention in gonadotropic regulation in patient with PCO. In addition, the degree of bromocriptine to inhibit LH secretion might be related to the dose or duration of its administration, or to the sensitivity of the patients. The mechanism of bromocriptine for marked LH suppression in PCO patients remains to be elucidated.