Hypothalamic-pituitary-testicular axis disruptions in older men are differentially linked to age and modifiable risk factors: The European Male Aging Study

CONTEXT The cause of declining testosterone (T) in aging men and their relationships with risk factors are unclear. OBJECTIVE To investigate the relationships between lifestyle and health with reproductive hormones in aging men. DESIGN Baseline cross-sectional survey on 3200 community - dwelling men aged 40 - 79 yr from a prospective cohort study in 8 European countries. RESULTS Four predictors were associated with distinct modes of altered function:- Age: lower free T (FT) (-3.12 pmol/L/ yr, p<0.001) with raised luteinizing hormone (LH) suggesting impaired testicular function. Obesity: lower total T (TT) (-2.32 nmol/L) and FT (-17.60 pmol/L) for BMI >/=25 - <30 kg/m(2) and lower TT (-5.09 nmol/L,) and FT (-53.72 pmol/L) for BMI >/=30 kg/m(2) (p <0.001 - 0.01, referent: BMI <25 kg/m(2)) with unchanged/decreased LH, indicating hypothalamus/pituitary dysfunction. Co-morbidity: lower TT (-0.80 nmol/L, p <0.01) with unchanged LH in younger men but higher LH in older men. Smoking: higher sex hormone binding globulin (SHBG) (5.96 nmol/L, p <0.001) and LH (0.77 U/L, p <0.01) with increased TT (1.31 nmol/L, p<0.001) but not FT, compatible with a resetting of T-LH negative feedback due to elevated SHBG. CONCLUSIONS Complex multiple alterations in the hypothalamic-pituitary-testicular axis function exist in ageing men against a background of progressive age-related testicular impairment. These changes are differentially linked to specific risk factors. Some risk factors operate independently of but others interact with age, in contributing to the T decline. These potentially modifiable risk factors suggest possible preventative measures to maintain T during in aging men.