Objective: Decline in growth hormone (GH) secretion and serum levels of insulin-like growth factor-1 (IGF-1) during ageing may be a causal factor in the development of osteopenia. The purpose of this study was to test the effects of GH-replacement therapy on bone metabolism and mineral density in healthy men over 40 years old.
Material: 18 healthy men aged 60.2 +/- 2.4 (avg +/- SEM) with mean body weight 78.6 +/- 4.6 kg and body mass index (BMI) 26.5 +/- 1.4 kg/m2. Diagnosis of growth hormone deficiency was based on serum IGF-1 levels below 200 micrograms/L (138.1 +/- 9.2), abolished GH nocturnal surge and diminished glucagon-stimulated GH secretion compared to reference group of young men (16.2 +/- 1.8 to 30.6 +/- 4.7 micrograms/L/hour; p < 0.02 and 10.8 +/- 1.0 to 44.1 +/- 15.3 micrograms/L/hour; p < 0.02 respectively). Nine healthy men aged 27.5 +/- 1.3 were recruited as a control subjects. Their body weight was 76.3 +/- 2.2 kg and BMI 21.3 +/- 0.6 kg/m2.
Methods: The subjects received human, recombinant GH (rhGH) daily subcutaneously during 12 months in dose individually adjusted to maintain optimal (280-350 micrograms/L) serum IGF-1 level. Initial dose was 0.125 IU/kg b.w./week. Before and after 6 and 12 months of therapy clinical and laboratory exams, including serum GH, IGF-1, calcium, phosphate, osteocalcin, glucose, insulin levels and alkaline phosphatase (AP) activity were obtained. Lumbar spine and femoral neck bone mineral density (BMD) were measured by dual-energy X-ray absorptiometry.
Results: rhGH administration for 12 months led to a significant increase in mean serum IGF-1 levels, from 138.1 +/- 9.2 to 279.4 +/- 26.3 micrograms/L (p < 0.001). Mean serum osteocalcin concentration rose from 19.4 +/- 1.7 to 34.4 +/- 4.7 micrograms/L (p < 0.004), and serum AP activity changed nearly significantly, from 78.0 +/- 4.8 to 88.1 +/- 7.2 U/L. Lumbar spine and femur neck BMD increased significantly after 12 months, from 1.092 +/- 0.05 to 1.119 +/- 0.06 g/cm2 (p < 0.05) and from 0.886 +/- 0.04 to 0.905 +/- 0.04 g/cm2 (p < 0.05), respectively.
Conclusion: Growth hormone replacement therapy in elderly men may be regarded as a method useful to protect against osteoporosis progression.