[Changes in sexual hormones in a male population over 50 years of age. Frequency of low testosterone levels and risk factors].

OBJECTIVES: To investigate the changes in sexual hormones in a selected male population older than 50 years of age. To assess the frequency of biochemical hypogonadism and which factors are related to testosterone levels.

PATIENTS AND METHODS: A Cross-sectional study was carried out on 230 Spanish men older than 50 years of age. Blood tests were performed including: total testosterone, SHBG, calculated free testosterone, dehidroepiandrosterone sulfate, androstendione, estradiol, bioavailable estradiol, FSH, LH, and prolactin. Clinical and socio-demographic backgrounds were investigated. The frequency of biochemical hypogonadism was established using total and free testosterone levels as diagnostic criteria. Factors that may influence testosterone levels were evaluated by univariate and multivariate statistical analysis, and a logistic regression model was used to determine which factors can predict biochemical hypogonadism according to free testosterone levels.

RESULTS: Age was associated with a significant decrease (p < 0.05) in total testosterone (0.6% per year), free testosterone (1.3% per year), dehydroepiandrosterone sulfate (1.8% per year) and bioavailable estradiol (0.69% per year). Moreover, an increase in SHBG, LH, and FSH was observed (p < 0.05). According to total testosterone levels, 4.8% of the men were hypogonadal, whereas 24.8% were hypogonadal when free testosterone was considered. In the univariate analysis, obesity, diabetes mellitus and hyperlipemia were related to lower total testosterone levels, while free testosterone levels were lower in men with sedentary life, lower levels of education, obesity or diabetes mellitus. In the multivariate analysis age, diabetes mellitus and obesity were inversely related to total and free testosterone levels. Free testosterone was also inversely related to hyperlipemia. For biochemical hypogonadism, simple logistic regression analysis selected age, sedentary life, obesity and diabetes mellitus. In the multivariate analysis age, obesity and diabetes mellitus had significant independent prognostic value.

CONCLUSIONS: Starting from 50 years of age, a significant age-related decrease in total testosterone, free testosterone, dehydroepiandrosterone sulfate and bioavailable estradiol is observed. The frequency of biochemical hypogonadism is higher when free testosterone levels are used for diagnosis. Total testosterone levels were related to age, diabetes mellitus and obesity. Free testosterone was related to age. diabetes mellitus, obesity and hyperlipemia. The probability of suffering low free testosterone levels increases with age, diabetes mellitus and/or obesity.