HORMONES, HORMONE RECEPTORS, AND AGING - III AGING AND HUMAN ENDOCRINE REGULATION

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Our clinical studies gather data on pituitary secretory function as it relates to gonadal, adrenal, thyroid, prolactin, and growth hormone regulation in normal aging humans. Our most recent findings were that growth hormone (GH) and somatomedin-C (Sm-C) responsiveness to GRF (growth hormone releasing factor) and ACTH and cortisol responsiveness to CRF (corticotropin releasing factor) are unaltered with age, whereas CRF mediated DHEA secretion is greatly reduced, suggesting independent regulation of cortisol and DHEA secretion. Basal and TRH stimulated Prl secretion are increased in older vs. younger men. We have recently measured testosterone, testosterone binding, and gonadotropins in a large group of men of various ages with and without chronic illness and have shown that there is modest, but significant, decrease in both total and free plasma testosterone (T) with age, accompanied by increased FSH, but not LH. The effects of illness were a profound (compared with effects of aging) lowering of free (but not total) T in patients with benign disease, and lowering of both free and total T in patients with cancer. Continuing studies address the interrelationships among circulating estrogens and androgens, incidence of cardiovascular disease, and known cardiovascular risk factors, such as lipoprotein profile, obesity, and body fat distribution. We plan studies of the temporal regulation and feedback sensitivity of the ACTH-adrenal axis in the coming year.