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CONTEXT: The cause of declining testosterone (T) in aging men and their relationships with risk factors are unclear. OBJECTIVE: The objective of the study was to investigate the relationships between lifestyle and health with reproductive hormones in aging men. DESIGN: This was a baseline cross-sectional survey on 3200 community-dwelling men aged 40-79 yr from a prospective cohort study in eight European countries. RESULTS: Four predictors were associated with distinct modes of altered function: 1) age: lower free T (FT; -3.12 pmol/liter.yr, P < 0.001) with raised LH, suggesting impaired testicular function; 2) obesity: lower total T (TT; -2.32 nmol/liter) and FT (-17.60 pmol/liter) for body mass index (BMI; > or = 25 to < 30 kg/m(2)) and lower TT (-5.09 nmol/liter) and FT (-53.72 pmol/liter) for BMI 30 kg/m(2) or greater (P < 0.001-0.01, referent: BMI < 25 kg/m(2)) with unchanged/decreased LH, indicating hypothalamus/pituitary dysfunction; 3) comorbidity: lower TT (-0.80 nmol/liter, P < 0.01) with unchanged LH in younger men but higher LH in older men; and 4) smoking: higher SHBG (5.96 nmol/liter, P < 0.001) and LH (0.77 U/liter, P < 0.01) with increased TT (1.31 nmol/liter, 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 aging 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 aging in men.

Original publication

DOI

10.1210/jc.2007-1972

Type

Journal article

Journal

The Journal of Clinical Endocrinology and Metabolism

Publication Date

07/2008

Volume

93

Pages

2737 - 2745

Addresses

Department of Endocrinology, Manchester Royal Infirmary, Oxford Road, Manchester, United Kingdom. frederick.wu@manchester.ac.uk

Keywords

European Male Aging Study Group, Testis, Hypothalamo-Hypophyseal System, Humans, Obesity, Testosterone, Luteinizing Hormone, Sex Hormone-Binding Globulin, Body Mass Index, Waist-Hip Ratio, Risk Factors, Cross-Sectional Studies, Alcohol Drinking, Comorbidity, Aging, Adult, Aged, Middle Aged, Male