Effects of Dihydrotestosterone on Lh Release Induced by Lh-Rh in Men

Abstract

In order to determine the effect of dihydrotestosterone on the feed-back mechanism of the hypothalamo-pituitary-testis axis, nine healthy subjects were subjected to LH-RH tests before and after treatment with 5\g=a\-DHT. A double antibody radio-immunoassay technique was used to measure the concentration of LH and FSH in the plasma. Our results clearly show that the pituitary LH release by LH-RH after pre-treatment with 5\g=a\-DHTis more pronounced. In the light of actual findings from several laboratories it is not possible to interpret clearly the results of our own experiments, and hence we advance only some hypotheses.Recent research has shown that in target organs, testosterone is converted into 5a-androstan-17/?-ol-3-one (dihydrotestosterone, DHT) its biological active form (Robel 1971). This change apparently takes place in the feed-back mechanism of the brain, the hypothalamus and the pituitary (Jaffe 1969;Tveter 1970;Massa et al. 1972; Zanisi et al. 1912b); consequently this steroid, together with testosterone, progesterone and oestradiol, could be involved in the mechanism controlling gonadotrophin release.Recent studies have shown that oestradiol, progesterone and testosterone (Fang et al. 1969; Sholiton 8c Werk 1969; Arimura 8c Schally 1971; Reeves et al 1971; Debeljuk et al. I972a,b; Davidson 1969; Guai et al. 1972; Zanisi et al. 1972a; Blake et al. 1972; D'Agata et al. 1974) influence the gonado¬ trophin response to synthetic LH-RH.These findings were the bases for our studies on the behaviour of plasma

Sex Steroid Control of Gonadotropin Secretion in the Human Male. I. Effects of Testosterone Administration in Normal and Gonadotropin-Releasing Hormone-Deficient Men*

“…Similarly, Sisk and Desjardins (63) found that LH pulse frequency was faster than that of castrates in some intact male ferrets and suggested that some animals were relatively insensitive to negative feedback by T. Taken together, these findings suggest that the role of gonadal steroids in the neuroendocrine control of gonadotropin secretion may vary considerably among individuals. Prior studies in normal men, using pharmacological doses of GnRH, have suggested that androgens do not inhibit, and may even enhance, the pituitary response to GnRH (2,4,6,9,64,65). The present data also demonstrate that serum LH levels rise in response to a pharmacological dose of GnRH during T administration in normal men.…”

The Effects of Gonadectomy and Oestradiol-17j3 on Pituitary Responsiveness to LH-RH in the Adult Male Marmoset (Callithrix jacchus)

“…Similarly, in the ovariectomized rhesus monkey, oestradiol-17/3 implants maintained for 13 days reduced LH release in response to LH-RH (21). Oestrogen can also impair pituitary response to a single injection of LH-RH in normal (19) and hypogonadal (40) women and in normal men (7).…”

“…Pre vious observations in man have shown that oestradiol-17/3 can impair pituitary responsiveness to LH-RH in males as well as in females (7,23,31). Since oestradiol-17/3 inhibits circulating LH levels in men (23,36), male rhesus monkeys (28) and marmosets (17), endogenous oestrogens may play a critical role in regulating pituitary LH release in primates of both sex, although it has been suggested (23) that the expression of oestrogen feedback at the level of the pituitary in men is different from that in women.…”

Gonadotrophin-Release Upon Intravenous Administration of a Long-Acting Analogue of Luteinizing Hormone-Releasing Hormone in Females With Increased Plasma-Androgens

“…An increase of LH-RH-induced gonadotrophin-secretion after pre-treatment with dihydrotestosterone has been reported in males (D'Agata et al 1975). The ef¬ fectiveness of elevated testosterone levels in suppressing basal and LH-RHstimulated secretion of gonadotrophins in males is however, well documented (Lee et al 1972;Sherins 8c Loriaux 1973;von zur Mühlen 8c Köbberling 1973).…”