Effects of human growth hormone on body composition in elderly men

Body composition changes progressively in mid and late adulthood. Lean body mass in men over 50 years old contracts at an average rate of -0.6% per year. Body weight tends to remain stable because of a reciprocal expansion of adipose mass. The shrinkage of the lean body mass reflects the atrophy of skeletal muscles, skin and visceral organs. Because growth hormone causes expansion of the lean body mass and contraction of the adipose mass, and because growth hormone secretion tends to diminish in late adulthood, it has been postulated that geriatric hyposomatotropism is a contributory cause to the body composition changes described above. The authors have tested this hypothesis by recruiting 45 independent men over 61 years old with plasma somatomedin C level below 0.35 U/ml, indicating little or no detectable growth hormone secretion. The 21-month protocol was as follows: baseline period 0-6 months, experimental period 6-18 months and post-experimental period 18-21 months. During the experimental period, 26 men (group I) received approximately 0.03 mg/kg of biosynthetic human growth hormone (hGH) subcutaneously 3 times a week, while 19 men (group II) received no treatment. Plasma somatomedin C was measured monthly. The following outcome variables were measured at 0, 6, 12 and 18 months: lean body mass, adipose mass, skin thickness (dermis plus epidermis), sizes of the liver, spleen and kidneys, the cross sectional areas of ten muscle groups, and bone density at 9 skeletal sites. Lean body mass and adipose mass were also measured at 21 months. In group I, hGH treatment raised the plasma somatomedin C level and maintained it in the range 0.5-1.5 U/ml.(ABSTRACT TRUNCATED AT 250 WORDS)