Decline of serum levels of free testosterone in aging healthy Chinese men.

Objective . To investigate the age-related change of serum androgen levels in healthy men and to define a cut-off value of serum testosterone for the diagnosis of androgen deficiency in the aging male. Method . 1080 healthy men aged 20 to &geqslant;70 years old were enrolled in Beijing, Shanghai, Xian and Chongqing. Luteinizing hormone (LH), follicle-stimulating hormone (FSH), total testosterone (T), calculated free testosterone (cFT), sex hormone binding globulin (SHBG), 17beta-oestradiol (E2), the T/LH ratio, and T/SHBG as a free testosterone index (FTI) were all determined. Results . Serum total T did not significantly decline, but the cFT, T/LH and FTI progressively decreased with aging. To determine androgen deficiency, the 10th percentile value of men 70 years. Conclusions . (i). While serum total T values do not decline with aging, the levels of cFT gradually decline with aging; (ii) when using the value of cFT of the 10th percentile of men aged 20 to 39 years as the cut-off point, the prevalence of androgen deficiency was <15% before the age of 50 years, and about 30% thereafter, approaching 45% after the age of 70 years; and (iii) in this study the values of T/LH paralleled those of cFT closely; therefore, T/LH could serve as a surrogate for cFT. [ABSTRACT FROM AUTHOR]