No discrete event marks a transition to male reproductive senescence; however, a number of investigations have suggested that male fertility and reproductive hormone secretion decrease with age, giving rise to the term male menopause. Nearly all studies of seminiferous tubular function and morphology have found evidence of an age-related deterioration including anatomical lesions, reduced semen quality, elevated serum levels of inhibin, and diminished fertility. The question of altered androgen secretion remains controversial with evidence both for and against age-related reductions in testosterone (T), free T, and/or DHT in multiple investigations. Much of this controversy probably stems from noncompar-able populations, especially with regard to confounding variables such as stress, illness, and medication use. Published findings to date agree that in healthy aging men there is a small but significant increase in basal levels of LH and a diminished T response to exogenous gonadotropin, suggesting an intrinsic loss of Leydig cell reserve. Moreover, there is evidence of a gradual loss of function of the hypodialamic/pituitary gonadotropic axis as well. Despite these changes, healthy aging men appear to maintain normal circulating total and free T and DHT levels, despite modest increases in sex hormone binding globulin (SHBG) and an small downward trend in serum androgens. Whether there are metabolic consequences such as altered body composition, muscle strengdi, and lipid profiles in the portion of the aging male population with larger androgen decrements requires further investigation.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism