Endocrine alterations in the aging male.
The recent increase in the elderly population, current health trends and awareness of age-related changes in the male endocrine system, have led to discussions about the role of the hormonal changes in the aging process in males. Better prevention and treatment of suboptimal health status and age-related diseases in aging men are based on an improved understanding of aging, particularly of the significance of age-associated hormonal changes. The aims of this study were 1) to evaluate the age dependence of the serum concentrations of the following important hormonal parameters in adult males using the IMMULITE 1 automated assay system (DPC, Los Angeles): testosterone, dehydro-epiandrosterone sulfate (DHEAS), estradiol (E2), sex hormone binding globulin (SHBG), lutropin (LH), follitropin (FSH), cortisol, prolactin, thyroid stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4) and the growth hormone-dependent parameters insulin-like growth factor (IGF-I) and IGF-binding protein-3 (IGFBP-3) and 2) to derive the following parameters: calculated free testosterone (cFT), ratio of calculated free testosterone to total testosterone (% cFT) and free androgen index (FAI). We found a significant decrease between the 21-30-year age group and the > 70-year age group for total testosterone (-42.4%), FAI (-65.5%), cFT (-60.0%), % cFT (-30.0%), DHEAS (-71.9%), E2 (-35.4%), TSH (-23.6%), IGF-I (-40.3%) and IGFBP-3 (-26.5%). Since the decreases in the FAI and cFT were greater than that of total testosterone and because these derived parameters reflect the biologically active fraction of testosterone, FAI and cFT are better markers for androgen deficiency in males. In contrast, a significant increase with age was observed for SHBG (+61.2%), LH (+40.0%), FSH (+98.3%) and cortisol (+54.2%). No significant alterations with age were observed for prolactin, fT3 and fT4. The study demonstrates that determining complete profiles of the androgenic, gonadotropic, adrenocortical, thyroid, pituitary and growth hormone/IGF endocrine axes in middle-aged and elderly men may be helpful in obtaining a correct clinical diagnosis for various hormonal disorders.