Central hypogonadism is a clinical condition, characterized by sexual symptoms and low serum testosterone levels, due to an impaired function of the hypothalamus or pituitary gland. Testosterone replacement therapy (TRT) is the standard treatment for hypogonadism, but it has some disadvantages. TRT is not a good option in men wishing to preserve fertility, nor in men with (a high risk of) prostate cancer, polycythemia, thrombophilia and severe cardiovascular disease. In this review, we discuss alternative treatments for central hypogonadism. If reversible causes are present, non-pharmacological interventions can be therapeutic. Gonadotropins are a good alternative to TRT when fertility is desired in the near future though they require frequent injections. Clomiphene citrate and tamoxifen seem to be a safe alternative for the treatment of functional central hypogonadism in men, as several studies reported a significant increase in testosterone levels with these drugs. However, their use is off-label and data supporting the efficacy of clomiphene citrate and tamoxifen on hypogonadal symptoms are insufficient. For this reason, clomiphene citrate and tamoxifen should not be used in routine clinical practice to treat sexual symptoms in men with central hypogonadism.

Sex hormone-binding globulin (SHBG) is the high-affinity binding protein for androgens and estrogens. According to the free hormone hypothesis, SHBG modulates the bioactivity of sex steroids by limiting their diffusion into target tissues. Still, the in vivo physiological role of circulating SHBG remains unclear, especially since mice and rats lack circulating SHBG post-natally. To test the free hormone hypothesis in vivo, we examined total and free sex steroid concentrations and bioactivity on target organs in mice expressing a human SHBG transgene. SHBG increased total androgen and estrogen concentrations via hypothalamic-pituitary feedback regulation and prolonged ligand half-life. Despite markedly raised total sex steroid concentrations, free testosterone was unaffected while sex steroid bioactivity on male and female reproductive organs was attenuated. This occurred via a ligand-dependent, genotype-independent mechanism according to in vitro seminal vesicle organ cultures. These results provide compelling support for the determination of free or bioavailable sex steroid concentrations in medicine, and clarify important comparative differences between translational mouse models and human endocrinology.

Article published by the Endocrine Society Article published by the Endocrine Society

Context: Secondary hypogonadism is common in aging men; its natural history and predisposing factors are unclear. Objectives: The objectives were 1) to identify factors that predispose eugonadal men (T ≥ 10.5 nmol/L) to develop biochemical secondary hypogonadism (T < 10.5 nmol/L; LH ≤ 9.4 U/L) and secondary hypogonadal men to recover to eugonadism; and 2) to characterize clinical features associated with these transitions. Design: The study was designed as a prospective observational general population cohort survey. Setting: The setting was clinical research centers. Participants: The participants were 3369 community-dwelling men aged 40–79 years in eight European centers. Intervention: Interventions included observational follow-up of 4.3 years. Main Outcome Measure: Subjects were categorized according to change/no change in biochemical gonadal status during follow-up as follows: persistent eugonadal (n = 1909), incident secondary hypogonadal (n = 140), persistent secondary hypogonadal (n = 123), and recovered from secondary hypogonadism to eugonadism (n = 96). Baseline predictors and changes in clinical features associated with incident secondary hypogonadism and recovery from secondary hypogonadism were analyzed by regression models. Results: The incidence of secondary hypogonadism was 155.9/10 000/year, whereas 42.9% of men with secondary hypogonadism recovered to eugonadism. Incident secondary hypogonadism was predicted by obesity (body mass index ≥ 30 kg/m²; odds ratio [OR] = 2.86 [95% confidence interval, 1.67; 4.90]; P < .0001), weight gain (OR = 1.79 [1.15; 2.80]; P = .011), and increased waist circumference (OR = 1.73 [1.07; 2.81], P = .026; and OR = 2.64 [1.66; 4.21], P < .0001, for waist circumference 94–102 and ≥102 cm, respectively). Incident secondary hypogonadal men experienced new/worsening sexual symptoms (low libido, erectile dysfunction, and infrequent spontaneous erections). Recovery from secondary hypogonadism was predicted by nonobesity (OR = 2.28 [1.21; 4.31]; P = .011), weight loss (OR = 2.24 [1.04; 4.85]; P = .042), normal waist circumference (OR = 1.93 [1.01; 3.70]; P = .048), younger age (< 60 y; OR = 2.32 [1.12; 4.82]; P = .024), and higher education (OR = 2.11 [1.05; 4.26]; P = .037), but symptoms did not show significant concurrent improvement. Conclusion: Obesity-related metabolic and lifestyle factors predispose older men to the development of secondary hypogonadism, which is frequently reversible with weight loss.

Context: Low testosterone (T) has been associated with incident metabolic syndrome (MetS), but it remains unclear if this association is independent of sex hormone binding globulin (SHBG). Estradiol (E2) may also be associated with MetS, but few studies have investigated this. Objective: To study the association between baseline sex steroids and the development of incident MetS and to investigate the influence of SHBG, body mass index (BMI) and insulin resistance on this risk. Methods: Three thousand three hundred sixty nine community-dwelling men aged 40–79 years were recruited for participation in EMAS. MetS was defined by the updated NCEP ATP III criteria. Testosterone and E2 levels were measured by liquid and gas chromatography/mass spectrometry, respectively. Logistic regression was used to assess the association between sex steroids and incident MetS. Results: One thousand six hundred fifty one men without MetS at baseline were identified. During follow-up, 289 men developed incident MetS, while 1362 men did not develop MetS. Men with lower baseline total T levels were at higher risk for developing MetS [odds ratio (OR) = 1.72, P < .001), even after adjustment for SHBG (OR = 1.43, P = .001), BMI (OR = 1.44, P < .001) or homeostasis model assessment of insulin resistance (HOMA-IR) (OR = 1.64, P < .001). E2 was not associated with development of MetS (OR = 1.04; P = .56). However, a lower E2/T ratio was associated with a lower risk of incident MetS (OR = 0.38; P < .001), even after adjustment for SHBG (OR = 0.48; P < .001), BMI (OR = 0.60; P = .001) or HOMA-IR (OR = 0.41; P < .001). Conclusions: In men, lower T levels, but not E2, are linked with an increased risk of developing MetS, independent of SHBG, BMI or insulin resistance. A lower E2/T ratio may be protective against developing MetS.

Androgen deficiency is associated with obesity, metabolic syndrome, and type 2 diabetes mellitus in men, but the mechanisms behind these associations remain unclear. In this study, we investigated the combined effects of androgen deficiency and high-fat diet (HFD) on body composition and glucose homeostasis in C57BL/6J male mice. Two models of androgen deficiency were used: orchidectomy (ORX) and androgen receptor knockout mice. Both models displayed higher adiposity and serum leptin levels upon HFD, whereas no differences were seen on a regular diet. Fat accumulation in HFD ORX animals was accompanied by increased sedentary behavior and occurred in spite of reduced food intake. HFD ORX mice showed white adipocyte hypertrophy, correlated with decreased mitochondrial content but not function as well as increased lipogenesis and decreased lipolysis suggested by the up-regulation of fatty acid synthase and the down-regulation of hormone-sensitive lipase. Both ORX and androgen receptor knockout exacerbated HFD-induced glucose intolerance by impairing insulin action in liver and skeletal muscle, as evidenced by the increased triglyceride and decreased glycogen content in these tissues. In addition, serum IL-1β levels were elevated, and pancreatic insulin secretion was impaired after ORX. Testosterone but not dihydrotestosterone supplementation restored the castration effects on body composition and glucose homeostasis. We conclude that sex steroid deficiency in combination with HFD exacerbates adiposity, insulin resistance, and β-cell failure in 2 preclinical male mouse models. Our findings stress the importance of a healthy diet in a clinical context of androgen deficiency and may have implications for the prevention of metabolic alterations in hypogonadal men.