ABSTRACT
Healthy aging in men progressively reduces testosterone availability to bone, muscle, brain, fat depots, immune tissue, and sexual organs (1). Free and bioavailable testosterone concentrations fall by 0.8% to 1.5% per year and are reduced by 30% by the seventh compared with third decade of life. Sexhormone binding globulin (SHBG) concentrations rise twofold in older males. Estradiol bioavailability declines along with that of testosterone, probably contributing to reduced bone density, elevated follicle-stimulating hormone (FSH) concentrations, and decreased prolactin concentrations. Although testis size and firmness diminish, spermatogenesis may be relatively preserved in elderly men.
