Background: The aim was to establish reference intervals for serum sex hormones in adult men in the Fangchenggang area of China.
Methods: Serum samples from 1,191 healthy male subjects, aged 20 - 69 years, were collected from the Fangchenggang Area Male Health and Examination Survey (FAMHES). Total testosterone (T), estrogen (E2), luteinising hormone (LH), follicle-stimulating hormone (FSH), and sex hormone-binding globulin (SHBG) were measured by electrochemiluminescence immunoassay (Elecsys). Free testosterone (FTc) was calculated from the concentrations of T, SHBG, and albumin.
Results: The total nonparametric reference intervals for male sex hormones in our study were 12.6 - 37.0 nmol/L for T, 0.24 - 0.69 nmol/L for FTc, 65.4 - 207.7 pmol/L for E2, 2.2 - 11.6 IU/L for LH, 1.8 - 16.5 IU/L for FSH, and 18.2 - 95.1 nmol/L for SHBG. Age had a significant positive association with LH (r = 0.218), FSH (r = 0.427), and SHBG (r = 0.427) and a negative association with FTc (r = -0.383) and E2 (r = -0.098), but no significant association with T after adjustment for BMI. The age-dependent reference intervals were also calculated. Higher T and FTc concentrations were found in men who smoke compared with non-smokers, while no significant differences were found in E2, LH, FSH, and SHBG. When stratified for the number of cigarettes smoked per day, we found that the distributions of serum T levels were significantly higher only in the smokers who smoked 11 or more cigarettes a day than the non-smokers. Unlike T, the distributions of serum FTc levels were significantly higher only in the smokers who smoked less than 11 cigarettes a day, while the FSH levels were significantly lower.
Conclusions: In clinical practice, single reference intervals can be used for men aged 20 - 69 years for T and E2 measured with the Elecsys method, but separate age-dependent reference intervals should be used for FTc, LH, FSH, and SHBG. In addition, distinct reference intervals for T should be established for non-smokers or smokers (1 - 10 cigarettes/day) and smokers (> or = 11 cigarettes/day).