[The effect of occult hyperprolactinemia (OHP) on gonadotropin secretion system]

The present study was conducted to investigate the effects of the transient increase of serum prolactin levels on the gonadotropin secretion system in patients with occult hyperprolactinemia (OHP). 216 cases of normoprolactinemic hypothalamic anovulatious were selected by LH-RH and TRH loading tests, and 5mg/day of bromocriptine was administered for more than 8 weeks. The effectiveness of the bromocriptine administration was estimated by the ultrasonic examination of the follicular development. The endocrinological backgrounds were compared between bromocriptine effective (154 cases, group A) and non-effective (62 cases, group B) patients. Serum prolactin levels 30min. after LH-RH and TRH loading (PRL30 in group A were significantly higher than those of group B (74.1 +/- 36.5 vs. 38.0 +/- 18.2ng/ml, p < 0.01). From this result, it was thought that many of the OHP patients were selected in group A. Serum LH levels 30min. after loading test (LH30) in group A also increased compared to those of group B (65.0 +/- 66.5 vs. 43.1 +/- 34.3mIU/ml, p < 0.02). The LH/FSH ratio before loading was also higher in group A (1.3 +/- 0.6) than that of group B (1.0 +/- 0.5, p < 0.02). This fact showed that group A also contained patients with hyper-LH hypothalamic anovulation, which is known as the endocrinological PCOD. There were also significant inverse correlations between serum levels of prolactin and FSH in group A (before loading values: r = 0.272, 30min. after loading: r = 0.224, p < 0.01). By the administration of bromocriptine, serum prolactin levels decreased both in group A and B, and the elevated serum LH/FSH ratio (1.0 +/- 0.4, p < = 0.02), LH30 (46.1 +/- 37.0mIU/ml, p < 0.005) also decreased significantly. Serum levels of FSH in group A increased significantly with treatment (before loading: 5.4 +/- 2.6-->6.2 +/- 2.0, 30min. after loading: 10.6 +/- 6.0-->14.6 +/- 9.9mIU/ml, p < 0.005). From these facts, it was concluded that FSH secretion was suppressed even by a slight increase of serum prolactin levels which was usually seen in the OHP, and bromocriptine administration was effective not only for the suppression of serum prolactin and LH levels, but also for the improvement of FSH secretion in the OHP patients.