J Clin Endocrinol Metab 43: 944, 1976 STUDY ON THE RELATIONSHIP BETWEEN PLASMA PROLACTIN LEVELS AND ANDROGEN METABOLISM IN MAN. G. Magrini, J.R. Ebiner, P. Burckhardt and J.P. Felber Division de Biochimie Clinique, Departement de Medecine, Centre Hospitalier Universitaire Vaudois, CHUV, 1011 Lausanne, Switzerland. ABSTRACT : The purpose of the study was to investigate the effect of hyperprolactinemia on the metabolism of androgens in man. A group of 6 normal men was treated for 4 consecutive days, on separate periods, with Sulpiride which is known to raise plasma prolactin (PRL) concentration. The effect of the treatment on plasma steroids was verified in basal conditions and under stimulation by HCG. In the controls, a parallel rise in testosterone ( T ) and dihydrotestosterone (DHT) was observed in response to HCG stimulation. In experimental hyperprolactinemia, the rise in T in response to HCG, similar to that of the controls, was accompanied by a markedly diminished rise in DHT. Similar results were observed in a patient with hyperprolactinemia following apparent accidental section of the pituitary stalk. These data demonstrate the interference of increased levels of PRL in the metabolism of testosterone into the active DHT form by 5°< -reductase. They suggest that this mechanism could possibly impair the gonadal function in man. In male patients, hypogonadism has been reported to be often associated with elevated plasma PRL levels, suggesting that it might have a direct effect on the gonadal function (l-5). Plasma gonadotrophins were often found to be normal. The patients suffer from impotence and present oligo- or azoospermia. The symptoms occur irrespective of the cause of hyperprolactinemia. "In vitro" evidence of an antigonadc— trophic action of hyperprolactinemia at the gonadal level has been demonstrated in women (6,7). The purpose of the present study was to investigate, in man, the interrelationship between low or high plasma PRL levels and the metabolism of androgen steroids, as reflected by T and DHT levels in peripheral plasma under basal conditions and exogenous gonadotrophin stimulation. MATERIALS AND METHODS The study was performed in 6 normal volunteers, aged 19 to 39, without any sexual problems. They were treated for 4 consecutive days (day 1 to 4 ) , on periods separated by 10-day intervals, with Sulpiride (Dogmatil Delagrange, 3 x 100 mg/day, p.o.), a drug known to stimulate plasma PRL levels, or with Bromocriptine (Parlodel Sandoz, 2 x Submitted March 25, 1976.

2.5 mg/day, p.o.), which has the opposite effect on PRL levels. The action of treatment on steroids was verified in basal conditions (day 1 to 3) and during stimulation by HCG (Pregnyl Organon, 2000 IU, i.m.) on days 3 and 4. Plasma samples were taken every day from day 1 to day 5. Plasma PRL was measured by radioimmunoassay, using the double-antibody separation (hPRL kit from Serono-Hypolab). 25 ng hPRL standard are equivalent to 1 mlU W.H.O. 71/222. In man, the normal range was 0.8 to 8 ng/ml. Plasma T and plasma DHT were determined by radioimmunoassay after extraction and chromatography as previously reported (8). RESULTS Fig. 1 shows the mean variations (difference from the initial value + SEM) in the plasma levels of T, DHT and PRL in the group of 6 subjects. In the control test, the basal values of PRL, T and DHT were 5-02 ng/ml + 1 . 1 (SEM), 4'970 + 570 pg/ml, and 256 + 29 pg/ml respectively. PRL levels did not change during the test and a good parallelism was found between T and DHT responses to HCG stimulation. During PRL stimulation with Sulpiride, basal levels of T increased (day 1 to day 3 ) , and the T response to HCG (day 5) was comparable to that of the controls.

944 The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 06 October 2015. at 19:57 For personal use only. No other uses without permission. . All rights reserved.

945

RAPID COMMUNICATIONS ? 2S0.

5000.

E

3000

2ISO. t

2 woo 5

••

£-1000.

o

SO.

1 1 5