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Growth Hormone and Sex Steroid Effects on Serum Glucose, Insulin, and Lipid Concentrations in Healthy Older Women and Men

Endocrine (T.M., S.M.H., M.R.B.) and Metabolism (J.D.S.) Sections, Laboratory of Clinical Investigation, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224; Geriatrische Klinik (T.M.), 9000 St. Gallen, Switzerland; Kronos Longevity Research Institute (S.M.H.), Phoenix, Arizona 85016; Department of Veterans Affairs, Baltimore Veterans Affairs Medical Center, Geriatrics Research, Education, and Clinical Center (J.D.S., M.R.B.), and the University of Maryland School of Medicine Claude D. Pepper Older Americans Independence Center (J.D.S.), Baltimore, MD 21201; Division of Endocrinology and Metabolism, Johns Hopkins University School of Medicine (M.R.B.), Baltimore, Maryland 21218; and Research Service (M.R.B.), Veterans Affairs Medical Center, Washington, DC 20422

Address all correspondence and requests for reprints to: Marc R. Blackman, M.D., Washington, D.C., VA Medical Center, Research Service (151), 50 Irving Street NW, Washington, D.C. 20422. E-mail: marc.blackman{at}va.gov.

Context: With aging, GH, IGF-I, and sex steroid concentrations and glucose tolerance decrease, and body fat and serum lipids increase.

Objective: The aim of the study was to assess GH and/or sex steroid administration effects on serum glucose, insulin, insulin sensitivity, and lipids in older individuals.

Design: A double-masked, 2 x 2 factorial, placebo-controlled, double-dummy design was used for the study.

Intervention: GH and/or sex steroid [transdermal estradiol plus oral medroxyprogesterone acetate in women (HRT); testosterone enanthate (T) in men] were administered for 6 months.

Participants: Healthy, community-dwelling women (n = 57) and men (n = 74) ages 65–88 yr (mean, 72 yr) participated in the study.

Main Outcome Measures: We measured serum glucose, insulin, and insulin sensitivity [quantitative insulin sensitivity check index (QUICKI) and insulin sensitivity index (ISI)] before and during an oral glucose tolerance test and lipid profiles.

Results: In women, GH did not alter oral glucose tolerance test 120 min or 2-h area under the curve (AUC) glucose values, but it increased 120 min insulin and AUC insulin. There were no significant effects of HRT or GH+HRT. ISI and QUICKI decreased after GH. In men, GH increased 120 min and AUC glucose and insulin AUC. GH+T increased 120 min glucose and glucose and insulin AUCs. T alone did not affect glucose or insulin. ISI decreased after GH and GH+T, whereas QUICKI decreased after GH. GH in women and men and GH+T in men decreased QUICKI by 4 wk. In women, HRT decreased total cholesterol and low-density lipoprotein (LDL)-cholesterol, and GH decreased LDL-cholesterol. In men, total cholesterol decreased after T and GH+T. LDL-cholesterol decreased after GH and GH+T. GH increased serum triglycerides.

Conclusions: GH administration to healthy older individuals for 6 months increased insulin resistance with moderately beneficial effects on lipids.