Effects of six-month administration of recombinant human growth hormone to healthy elderly subjects

Abstract

In aging, both changes in body composition and a decrease in GH secretion are observed. While recombinant human GH (rhGH) therapy was shown to be effective in GH-deficient adults, its effects on normal aging are controversial. This study addressed the effects of six-month administration of low dosages of rhGH in a group of 5 healthy elderly subjects (age range 71–86 years). All subjects received 2 IU rhGH (Saizen, Serono) × 2/week s.c., which was approximately 0.03 mg/kg/week, and were examined before and 1, 3, and 6 months after the start of the therapy, as well as 3 months after therapy was suspended. Hormonal, metabolic and biochemical parameters, as well as bone density at the forearm level, body composition and muscle strength, assessed by isokinetic exercises, were evaluated at each scheduled visit. After the start of the therapy, there was an average 9±3 % increase (median 8%) in IGF-I levels (IGF-I basal: 145.6±9 ng/mL, IGF-I peak: 176.0±10; p<0.001). An increase in lean body weight, a decrease in fat (p<0.05), and an improvement in muscle strength (p<0.01) were recorded. No significant variation was observed in the metabolic parameters. During rhGH therapy, an increase in both bone resorption and formation parameters, and a slightly decreasing trend in bone density were noted. In conclusion, low dosages of rhGH in healthy elderly subjects seem to determine some physiological effects, such as a slight increase in IGF-I levels, which in turn may be responsible for the positive effects on body mass composition and muscle strength, without producing side effects. On the other hand, 6-month subcutaneous rhGH therapy at the dosage employed was unable to improve bone density.