Changes of prolactin secretion following long-term danazol application.

Patients (n = 10) with endometriosis or fibrocystic mammary disease were treated with an oral dose of 4 x 200 mg danazol for 6 months. Prolactin and gonadotropin secretion was evaluated before, and in some of them during 1, 3, and 6 months of therapy, as well as 4 weeks after discontinuation of the steroid. Prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol, and progesterone were measured before a bolus of 10 mg metoclopramide and 25 micrograms LH-releasing hormone (LH-RH) had been given. The serum concentrations of prolactin and LH were estimated 25 minutes and those of FSH 45 minutes thereafter. Basal and stimulated serum prolactin levels, measured during the luteal phase of the control cycle preceding danazol application, decreased continuously, reaching serum concentrations seen during the early follicular phase of the cycle. This was paralleled by a decrease of estradiol and a lack of progesterone secretion. While basal and LH-RH-stimulated LH was practically unchanged, basal and stimulated FSH showed a significant increase. Within 4 weeks of discontinuation of the drug all hormonal parameters were similar to pretreatment values. The data presented may explain the beneficial effect of the drug on fibrocystic mammary disease, i.e., by the decrease of serum and pituitary prolactin. The selective increase of FSH secretion is unclear but may reflect the lack of negative feedback mechanisms of follicular inhibin.