Restoration of oestrogen-positive feedback effect on LH release in women with prolactinoma by transsphenoidal surgery

Abstract

The effect of hyperprolactinemia on the hypothalamo-pituitary axis was assessed by i.v. injection of 100 .mu.g LHRH in 7 women with prolactinoma before and 3 mo. after normalization of the Prl level by transsphenoidal surgery. A dose of 20 mg of conjugated estrogen (Premarin) was also injected i.v. into patients with prolactinoma before and 4 mo. after surgery, and the serum LH levels were determined serially for 120 h after the injection. Surgical treatment caused significant reduction of the mean (.+-. SE) serum prolactin (Prl) level from 123.3 .+-. 7.8 to 19.4 .+-. 5.6 ng/ml. The differences in the basal levels of LH [luteinizing hormone] (11.3 .+-. 2.2 to 8.6 .+-. 1.5 mIU/ml), FSH (8.3 .+-. 2.4 to 10.6 .+-. 3.7 mIU/ml) and estradiol (26.6 .+-. 8.6 to 37.5 .+-. 5.5 pg/ml) before and 4 mo. after surgery were not significant. An exaggerated LH response to LHRH in untreated prolactinoma patients was also observed after surgical treatment. After surgical treatment, patients showed LH release with a peak between 48 and 72 h after the injection of Premarin, whereas before treatment they did not show any LH discharge. The mean percent increase in LH between 48 and 72 h was also significantly higher after operation than before operation. The hyperprolactinemia in prolactinoma patients may cause an impaired positive feedback effect of estrogen on LH release and this derangement can be reversed by reduction of the Prl level by adenomectomy.