One year of GH replacement therapy with a fixed low-dose regimen improves body composition, bone mineral density and lipid profile of GH-deficient adults

OBJECTIVE: We have studied the effects on body composition and metabolism of a fixed low dose of growth hormone (GH), 0.6 IU (0.2 mg)/day, administered for 12 months to GH-deficient (GHD) adults. DESIGN AND METHODS: Prospective open-label study, using 18 GHD patients (11 women, 7 men; aged 21-58 years). All investigations were performed at baseline and after 12 months. Body composition was determined by dual energy X-ray absorptiometry. RESULTS: Total body fat decreased (-1.74+/-2.87%) and lean body mass (LBM) increased (1.27+/-2.08 kg) after therapy (P < 0.05). Changes in truncal fat did not reach statistical significance, but a decrease varying from 0.72 to 2.78kg (1 to 8.7%) was observed in 13 (72%) patients. Bone mineral density (BMD) increased at lumbar spine, total femur and femoral neck (P < 0.05). Levels of total and low-density lipoprotein (LDL)-cholesterol were lower after therapy (P < 0.05), and their changes were directly associated with values at baseline. Insulin levels increased and the insulin resistance index worsened at 12 months (P < 0.05). Median IGF-I s.d. score was -4.30 (range, -11.03 to -0.11) at baseline and -1.73 (range, -9.80 to 2.26) at 12 months. Normal age-adjusted IGF-I levels were obtained with therapy in 5 of 11 patients who had low IGF-I levels at baseline. Changes in IGF-I levels were not correlated with any biological end point, except changes in LBM (r = 0.53, P = 0.02). Side effects were mild and disappeared spontaneously. CONCLUSIONS: One-year of a fixed low-dose GH regimen in GHD adults resulted in a significant reduction in body fat, total cholesterol and LDL-cholesterol, and a significant increase in LBM and BMD at lumbar spine and femur, regardless of normalization of IGF-I levels. This regimen led to an elevation of insulin levels and a worsening of the insulin resistance index.