Long-term administration of thyrotropin-releasing hormone and its effect on gonadotropin secretion in eumenorrheic...

Thyrotropin-releasing hormone (TRH) was administered orally in doses of 60 mg/day to six women for two consecutive menstrual cycles. Daily serum samples were obtained for radioimmunoassay of luteinizing hormone, follicle-stimulating hormone, prolactin (PRL), and 17beta-estradiol secretory response. TRH was ineffective in interfering with normal gonadotropin and estradiol secretion, and failed to inhibit ovulation. The length of the luteal phase was not affected by TRH in the two cycles of treatment as demonstrated by basal body temperature, pregnanediol excretion, and endometrial biopsy. Long-term TRH administration induced an elevation of PRL serum levels that were not persistent and showed wide spikes. From these studies it is concluded that oral TRH at a dosage of 60 mg/day is unable to modify gonadotropin secretion and ovarian responsiveness in normally menstruating women.