THE EFFECTS OF TESTOSTERONE AND ITS 5α-REDUCED METABOLITES ON PITUITARY RESPONSIVENESS TO GONADOTROPHIN-RELEASING HORMONE (Gn-RH)

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Abstract
The effects of androgens on gonadotropin release in response to gonadotropin-releasing hormone (Gn-RH) stimulation were studied in vitro. Hemipituitaries of mature male rats were preincubated for 90 min with T [testosterone], DHT [dihydrotestosterone], 3.alpha.- or 3.beta.-diol (4 ng or 4 .mu.g/ml medium), and the incubation continued for 240 min after adding Gn-RH (1 ng/ml medium). Gn-RH caused a 4-5-fold rise in the secretion of LH [luteinizing hormone] and a 2-fold rise in FSH [follicle stimulating hormone] secretion. The effect of the androgens was dose-dependent. At low levels, T and DHT exerted no effect on Gn-RH-stimulated gonadotropin release, whereas the 2 androstanediols (3.alpha.- and 3.beta.-diol) augmented the Gn-RH stimulation of both gonadotropins, though preferentially LH. With high doses of androgens, the results showed: no effect of T; DHT suppression of the Gn-RH-stimulated FSH release; suppression of Gn-RH stimulation by 3.alpha.- and 3.BETA.-diol regarding both LH and FSH. T exerts through its reduced metabolites a feedback effect on the pituitary gland responsiveness to Gn-RH stimulation.