EFFECTS OF RECOMBINANT HUMAN GROWTH-HORMONE ON METABOLIC INDEXES, BODY-COMPOSITION, AND BONE TURNOVER IN HEALTHY ELDERLY WOMEN

We conducted a controlled trial of recombinant human GH (rhGH) in 27 healthy elderly women (66.7 +/- 3.0 yr), of whom 8 took a stable dose of replacement estrogen throughout the study (plus estrogen group). Hormone or placebo was given as a single daily injection. A total of 19 women were assigned to receive rhGH at an initial daily dose of 0.043 mg/kg BW. After several weeks, 50% dose reductions were necessitated by side-effects. The last 7 subjects to be enrolled began treatment at this reduced level. A total of 13 women assigned to rhGH and 14 women assigned to placebo completed 6 months of drug treatment. In the rhGH group, 6 women took estrogen; thus, the effects of rhGH were assessed separately by estrogen status. Circulating insulin-like growth factor-I (IGF-I) levels were similar at baseline (rhGH, 133 +/- 40.4 mu g/L; placebo, 128 +/- 13). rhGH increased IGF-I and IGF-I-binding protein-3 (IGFBP-3) in all subjects [6 month IGF-I in plus estrogen women, 230 +/- 25.4 mu g/L; in those not receiving estrogen (minus estrogen), 308 +/- 21.3]. No changes in IGF-I or IGFBP-3 occurred with placebo (IGF-I, 144 +/- 21.3 mu g/L). Skinfold thickness measurements showed an 11% decrease in fat mass (P < 0.005) and a 9% decrease in percent fat after 6 months of rhGH treatment. No significant difference in nitrogen balance was seen in either group at 6 months, but rhGH increased creatinine clearance by 9.2% (P < 0.05). rhGH dramatically increased markers of bone turnover, with more pronounced effects in minus estrogen women. Hydroxyproline excretion increased by 20% and 80%, and pyridinoline excretion increased by 44% acid 75% in plus and minus estrogen subgroups, respectively. Osteocalcin concentrations increased by more than 60% in minus estrogen women (P < 0.05), but did not change in the plus estrogen group. No changes were observed in circulating type I procollagen extension peptide in either group, and no change in any turnover marker was seen in the placebo group, rhGH did not alter blood pressure or circulating L-T-4 levels, but a transient increase in serum T-3 was observed in the minus estrogen group at 3 months. rhGH decreased low density lipoprotein cholesterol in the minus estrogen group, but otherwise no significant changes in circulating lipoproteins or fibrinogen were observed. Eight women assigned to rhGH and 14 placebo-treated women remained on blinded treatment through 12 months. Analysis of this cohort showed persistence of the 6 month changes in IGF-I, IGFBP-3, and bone turnover markers. rhGH did not increase bone mineral density at the lumbar spine or hip, but the placebo group experienced 1.7% and 3.0% decreases in bone mineral density at the trochanter and Ward's triangle. We conclude that rhGH can be administered to healthy elderly women without obvious adverse effects on major cardiovascular risk factors, and the effects of such treatment are modulated by concurrent estrogen replacement therapy, rhGH is a powerful initiator of bone remodeling, but alone is unlikely to achieve major improvement in bone mass. The clinical utility of rhGH in elderly women is constrained by a high prevalence of side-effects, particularly fluid retention and carpal tunnel syndrome.