Strength and its relationship to changes in fat-free mass, total body potassium, total body water and IGF-1 in adults with growth hormone deficiency:effect of treatment with growth hormone

The present investigation examined changes in strength in growth hormone de ficient (GHD) adults following treatment with recombinant human growth horm one (rhGH), and assessed their relationship to changes in fat-free mass (FF M), total body potassium (TBK), total body water (TBW), the concentration o f TBK and TBW per kg FFM, and insulin like growth factor-1 (IGF-I). The inv estigation was double-blind and placebo-controlled for a period of 6 months ; this was followed by a period of open treatment for a Further 6 months. P atients were assigned randomly to experimental (E) and control (C) groups. In the first 6 months group E received rhGH and group C placebo; in the sec ond 6 months both groups received rhGH. Serial data were analysed for 23 ma les (11 group E, 12 group C) and 20 females (10 group E, 10 group C). Body composition was assessed by dual energy X-ray absorptiometry, TBK and TBW. Muscle strength was recorded for arm flexion, leg extension and hand grip. Significant increases in FFM occured in the first 6 months in group E (2.3 kg males, 1.4 kg females) and in the second 6 months in group C (2.4 kg mal es, 1.4 kg females). There was a modest increase in absolute strength with time, although only three increments were significant (knee extension in gr oup E males and arm flexion in groups E and C females), all of which occurr ed during the 6-12 month period. Allometric scaling did not improve the ide ntification of significant increments of strength. The mean concentrations of TBK (males 57.0-58.6, females 51.4-53.9 mmol) and TBW (males 0.65-0.69, females 0.65-0.68 1) per kg FFM, were significantly smaller at all stages o f the trial than the reference values, suggesting that treatment had not fu lly normalized these variables. Likewise, the relationship between most of the increments of regional and total strength, and the corresponding increm ents of FFM, were generally poor and not significant. It was concluded that the reduced concentrations of TBK and TBW per kg FFM, which may be the eff ect of an inappropriate dose regime or mode of delivery, may, in part, cont ribute to the anomaly between increases in strength and FFM.