Episodic luteinizing hormone release in hyperprolactinemic women

Episodic luteinizing hormone (LH) secretion was studied in 16 hyperprolactinemic women (microprolactinoma, 12; idiopathic, 4) with amenorrhea of 1.4 to 7years’ duration. Blood samples obtained through an indwelling venous catheter at 20-minute intervals over 5hours were assayed for LH, follicle-stimulating hormone (FSH), prolactin (PRL), and estrogen (E) (selected samples). LH pulse patterns were divided arbitrarily into high-amplitude release (LH pulse>10 mIU/ml) (n=7), low-amplitude release (LH pulse0.02), whereas mean percentages of secretory increment were 155% and 62%, respectively. Mean LH concentrations in the high-amplitude (18.0±0.8 mIU/ml), low-amplitude (13.2±0.6 mIU/ml), and no-pulse groups (7.5±0.2 mIU/ml) differed significantly (P>0.02). Despite the different pulse patterns, mean serum FSH, PRL, and total E concentrations were similar. The lack of episodic LH release and/or low infrequent LH release could account for the absence of cyclic hypothalamic pituitary ovarian function, although other mechanism(s) may be operative in women with augmented LH secretory pulses.