Molecular profiling of the human testis reveals stringent pathway-specific regulation of RNA expression following gonadotropin suppression and progestogen treatment.

Gonadotropin withdrawal induces changes in gene expression in all 3 major cell types of the testis. Knowledge of the genes affected, in both the presence and absence of additional progestogen, will give insight into the regulation of human testicular function and aid development of novel contraceptive methods. We have undertaken a whole-genome analysis of RNA expression in testicular biopsies from normal men and after 4 weeks of gonadotropin suppression induced by gonadotropin-releasing hormone antagonist plus testosterone administration sufficient to cause marked suppression of spermatogenesis. Microarray analysis shows that interindividual variability is markedly low, and the response to treatment is focused on a small subset of genes particularly related to pathways in steroidogenesis and cholesterol biosynthesis or metabolism, the Leydig cell gene INSL3, and genes involved in early meiosis or Sertoli-germ cell junctions. These changes in expression were confirmed by quantitative reverse transcriptase polymerase chain reaction. No major changes in gene expression were identified in men additionally treated with a progestogen, although FLJ35767, an expressed sequence tag that is expressed in the germ cell compartment, did show a small but significant additional effect of progestogen. Overall, the results of this investigation disclose a remarkably stringent regulation of testicular gene expression, revealing the genes most sensitive to gonadotropin withdrawal, and might reflect the most labile pathways in the regulation of testicular function.

7alpha-methyl-19-nortestosterone (MENT) vs testosterone in combination with etonogestrel implants for spermatogenic suppression in healthy men.

Testosterone with a progestogen can suppress spermatogenesis for contraception. The synthetic androgen 7alpha-methyl-19-nortestosterone (MENT) may offer advantages because it is resistant to 5alpha-reduction and is therefore less active at the prostate. This study aimed to investigate MENT implants in combination with etonogestrel on spermatogenesis, gonadotropins, and androgen-dependent tissues in comparison with a testosterone/etonogestrel regimen. Healthy men (n = 29) were recruited and randomized to receive 2 etonogestrel implants with either 600-mg testosterone pellets repeated every 12 weeks or 2 MENT implants for up to 48 weeks. Testosterone concentrations in the testosterone group remained in the normal range. Subjects with 2 MENT implants showed peak MENT levels at 4 weeks with testosterone concentrations of 2 nmol/L. Sperm concentrations fell rapidly to less than 1 x 10(6)/mL at 12 weeks in 8 of 10 subjects in the MENT group and 13 of 16 subjects in the testosterone group with equally suppressed gonadotropins. Thereafter, suppression was not maintained in the MENT group, and 6 men noted loss of libido. Fourteen men completed 48 weeks of testosterone treatment, and all became azoospermic. Hemoglobin concentrations rose, and high density lipoprotein-cholesterol (HDL-C) fell in both groups. The MENT group showed a fall in prostate-specific antigen with no change in bone mass. MENT with a progestogen can achieve rapid suppression of spermatogenesis similar to testosterone, but this promising result was not sustained due to a decline in MENT release from the implants. This dose of testosterone, compared with previous studies using a lower dose with a higher dose of etonogestrel, had nonreproductive side effects without any increase in spermatogenic suppression. These data indicate the importance of the doses of progestogen and testosterone for optimum spermatogenic suppression while minimizing side effects.

A diurnal variation in testicular hormone production is maintained following gonadotrophin suppression in normal men.

OBJECTIVE: A diurnal variation in serum testosterone in adult men is well recognized, but whether this occurs during exogenous testosterone administration and the degree to which it is endogenous to the testis is unclear. DESIGN: A clinical research centre investigation of testicular function in normal men. PATIENTS: Twenty normal men were recruited, 10 of whom were investigated during administration of testosterone with etonogestrel to suppress gonadotrophin secretion. MEASUREMENTS: Hourly blood samples were taken over 24 h for measurement of testosterone, inhibin B, LH, FSH and cortisol. Urinary excretion of testosterone and the testicular steroid epitestosterone was also measured. RESULTS: In the controls, a diurnal variation in serum testosterone and LH but not FSH was detected. The treated group had similar testosterone concentrations but showed no diurnal variation. Periodicity was also detected in inhibin B concentrations in 5 of the controls and in 9 of the treated group, who also showed synchrony not seen in the controls. Both groups showed diurnal variation in cortisol. Urinary testosterone excretion did not show a diurnal variation in either group, but this was apparent for epitestosterone with a morning peak in both groups despite the markedly lower excretion in the treated men. CONCLUSIONS: The diurnal variation of testosterone in normal men is due to a change in secretion rather than in clearance and is largely LH driven. An endogenous rhythm in both testicular steroidogenesis (epitestosterone) and Sertoli cell function (inhibin B) is also present.

Direct effect of progestogen on gene expression in the testis during gonadotropin withdrawal and early suppression of spermatogenesis.

CONTEXT: Testicular production of steroids and gametes is under gonadotropin support, but there is little information as to the molecular mechanisms by which these are regulated in the human. The testicular response to gonadotropin withdrawal is important for the development of effective contraceptive methods. OBJECTIVE: Our objective was investigation of expression of genes in the normal human testis reflecting steroidogenesis, Sertoli cell function, and spermatogenesis after short-term gonadotropin withdrawal and the effects of activating testicular progesterone receptors. DESIGN AND SETTING: We conducted a randomized controlled trial at a research institute. PATIENTS: Thirty healthy men participated. INTERVENTIONS: Subjects were randomized to no treatment or gonadotropin suppression by GnRH antagonist (cetrorelix) with testosterone (CT group) or with additional administration of the gestogen desogestrel (CTD group) for 4 wk before testicular biopsy. Gene expression was quantified by RT-PCR. RESULTS: Both treatment groups showed similar suppression of gonadotropins and sperm production and markedly reduced expression of steroidogenic enzymes. Addition of progestogen in the CTD group resulted in reduced expression of 5alpha-reductase type 1 compared with both controls and the CT group. Inhibin-alpha and the spermatocyte marker acrosin-binding protein were significantly lower in the CTD but not CT groups, compared with controls, but did not differ between treated groups. Men who showed greater falls in sperm production also showed reduced expression of these three genes but not of the spermatid marker protamine 1. CONCLUSIONS: These data provide evidence for direct progestogenic effects on the testis and highlight steroid 5alpha-reduction and disruption of spermiation as important components of the testicular response to gonadotropin withdrawal.

Male hormonal contraception: a safe option?

Hormonal male contraception is based on the administration of testosterone alone or more likely with a progestogen. Testosterone has been used for several decades for the treatment of male hypogonadism, with an excellent safety record. Use as part of a contraceptive regimen by healthy people for prolonged periods will necessitate careful re-examination of safety issues. Although potential male contraceptive regimens have been investigated for many years, there have been mostly small-scale studies unable to assess safety. This is now changing, with larger studies of regimens underway. This, and the increasing involvement of the pharmaceutical industry, means that much more data will shortly be forthcoming and it is hoped that this will also provide valuable information relevant to normal male health. The main areas of interest are the cardiovascular system and the prostate, but bone health and body composition are also important, as are behavioral and psychologic aspects. The development of this field also allows the investigation of potential health benefits, which may be related to the use of synthetic androgens with tissue-selective metabolism or action.