Physical repercussions of childhood-onset growth hormone (GH) deficiency and hGH treatment in adulthood.

Abstract

The aim of this study was to evaluate the physical condition of young adults with childhood-onset growth hormone deficiency (GHD) before and after 6 months of hGH therapy. Ten men and three women, aged 22.3 +/- 3.3 years, previously treated with hGH for 8.6 +/- 4.07 years at a dose of 0.5 IU/kg/week with a minimun of 2.5 years without treatment at the time of study, were studied. Nine patients presented isolated GHD and four patients had combined pituitary hormone deficiencies; they were treated with hGH at a dosage of 0.125 IU/kg/week for the first month and 0.25 IU/kg/week for the following 5 months. The tests performed were: exercise test, heart rate, rating of perceived exertion, blood lactate analysis, jump test and hand grip. Body composition was also analyzed using Holtain Body Analysis. Skinfold thickness was measured at four sites (triceps, biceps, subscapular and suprailiac). After 6 months of treatment a significant increase in lean body mass (42.0 +/- 7.72 to 46.2 +/- 8.01 kg, p = 0.004) and decrease in fat mass (19.6 +/- 10.01 to 16.1 +/- 10.79 kg, p = 0.01) were observed. The initial physical condition of these patients was lower than expected, and improved after treatment with an increase in maximum oxygen consumption from 2.0 +/- 1.2 to 2.33 +/- 0.68 l x min(-1) (p = 0.01). Maximum heart rate increased significantly from 189 +/- 14.8 to 193 +/- 11.7 beats x min(-1) (p = 0.03). No modifications were observed in anaerobic threshold (4 mmol x l(-1)). Only slight, non-significant increases were observed in jump and strength tests. We conclude that a) adults with childhood-onset growth hormone deficiency present a deficient physical condition and lower than expected for age and sex; b) this condition improves after 6 months of treatment, particularly in the aerobic aspect; c) changes observed in strength tests were discrete and of little significance; and d) the increase observed in lean body mass plays an important role in these changes. Further studies investigating GH action on maximum oxygen consumption are required, once its basic mechanism of action has been determined, either in the heart or peripheral factors.