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

The effects of hyperprolactinaemia on the hypothalamo-pituitary axis by iv injection of 100 micrograms luteinizing hormone releasing hormone (LRH) in 7 women with prolactinoma before and 3 months after normalization of the Prl level by transsphenoidal surgery. A dose of 20 mg of conjugated oestrogen (Premarin) was also infected iv into patients with prolactinoma before and 4 months 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. But the differences in the basal levels of HL (11.3 +/- 2.2 to 8.6 +/- 1.5 mIU/ml), FSH (8.3 +/- 2.4 to 10.6 +/- 3.7 mIU/ml) and oestradiol (26.6 +/- 8.6 to 37.5 +/- 5.5 pg/ml) before and 4 months after surgery were not significant. An exaggerated LH response to LRH 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. These results suggest that the hyperprolactinaemia in prolactinoma patients may cause an impaired positive feedback effect of oestrogen on LH release and that this derangement can be reversed by reduction of the Prl level by adenomectomy.