Effects of Short Term Administration of Recombinant Human Growth Hormone to Elderly People*

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Abstract
We evaluated the effects of recombinant human GH (rhGH) in 16 men and women more than 60 yr of age. After 10 days of dietary equilibration and control collections, subjects were randomly assigned to receive 0.03, 0.06, or 0.12 mg/kg rhGH by daily injection for 7 days. A brisk rise in circulating somatomedin-C (insulin-like growth factor-I) occurred in all subjects, and this rise was dose dependent. rhGH produced striking changes in nitrogen retention, sodium excretion, and the parathyroid-vitamin D axis. Twenty-four-hour urinary nitrogen excretion decreased from 8.00 .+-. 0.33 to 5.01 .+-. 0.33 g (P < 0.001), and sodium excretion decreased from 45.9 .+-. 2.96 to 21.2 .+-. 3.48 mmol/day (P < 0.001). Serum calcium concentrations did not change, but serum inorganic phosphorus levels of 1.08 .+-. 0.04 mmol/L at baseline increased significantly after rhGH treatment to 1.33 .+-. 0.04 mmol/L (P < 0.001). Increases were also observed in circulating PTH (53.2 .+-. 6 vs. 39.5 .+-. 4.2 ng/L P < 0.01) and calcitriol (82.8 vs. 65.8 pmol/L; P < 0.05). A rise is serum osteocalcin (10.3 .+-. .86 vs. 8.0 .+-. 0.5 .mu.g/L; P < 0.05) was accompanied by increased urinary excretion of hydroxyproline (628 .+-. 63 vs. 406 .+-. 44 .mu.mol/day; P < 0.01). Despite the reduction in sodium excretion, marked increases were observed in urinary calcium (6.04 .+-. 0.97 vs. 3.27 .+-. 0.40 mmol/day; P < 0.01). rhGH significantly impaired oral glucose tolerance and reduced insulin sensitivity, but was otherwise well tolerated and produced no systematic changes in weight or blood pressure. The results of this study indicate that rhGH requires further study as a potential agent for attenuating or reversing the loss of muscle and bone in elderly people.