Abstract. In hyperprolactinaemic patients with amenorrhoea, pulsatile secretion of LH is reported to be infrequent or absent. For further assessment of the effect of prolactin (Prl) on LH pulsatility, the serum gonadotrophin concentration was determined at 15 min intervals for 180 min in 12 patients with prolactinomas before treatment and in 6 patients who showed normalization of the Prl level after trans-sphenoidal surgery.
Surgical treatment caused a significant reduction (P < 0.05) of the mean (± se) serum Prl level from 519 ± 152 to 9.2 ± 1.4 ng/ml. The mean LH level (7.3 ± 1.2 mIU/ml) before treatment was significantly increased (P < 0.05) after trans-sphenoidal surgery (12.7 ± 2.4 mIU/ml). An LH spike was defined as an LH concentration that exceeded the mean LH level over the study period by 2 sd of the intra-assay variation, achieving a level of above 10 mIU/ml. LH spikes were observed in 2 of 12 patients (16.7%) before treatment, and in 5 of 6 patients (83.3%) after trans-sphenoidal surgery, the difference being significant (P < 0.05).
These results suggest that hyperprolactinaemia in prolactinoma patients may cause impaired LH pulsatile secretion and that this derangement can be reversed by reduction of the Prl level by adenomectomy.