Several studies have shown that total and free plasma testosterone levels begin to decline between 50 and 60 years of age. In part, this conflict may reflect disagreement in definitions of healthy aging. In any case, increases in both FSH and LH levels in some older men suggest at least a partial decline in testicular function. In other men, aging is accompanied by a decrease in the LH level and testosterone pulse frequency and by increased sensitivity of the hypothalamic-pituitary axis to inhibition by androgens. Many bodily changes occur in aging males that could be directly or indirectly associated with declining testicular function.
Decreases occur in bone density, lean body mass, muscular strength, and hematopoiesis.
Studies in younger, eugonadal males have shown that supraphysiological doses of testosterone, particularly when bolstered by physical training, lead to increased muscle mass and strength.