Comparison of measures of body composition in a trial of low dose growth hormone replacement therapy

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Abstract
OBJECTIVE We assessed the effects of the administration of low dose growth hormone in growth hormone deficient adults on body composition and physical performance. We compared the validity of different measures of body composition in GH treated adults. DESIGN An uncontrolled longitudinal study of eight patients with GH deficiency who were treated with 4 units of biosynthetic growth hormone (Norditropin), three times a week. Subjects were studied for 8 weeks. PATIENTS Eight patients with acquired growth hormone deficiency as defined by <5mU/1 GH following standard provocative investigations in whom other hormone replacement was optimized. MEASUREMENTS IGF‐I was measured on day 1 and after 4 and 8 weeks of treatment with recombinant human growth hormone. Body composition was estimated by dual energy X‐ray absorptiometry, bioelectrical impedance, skinfold anthropometry, total body potassium measurement and by computerized tomography of a representative cross‐sectional area of thigh on day 1 and following 8 weeks of treatment. Exercise capacity was measured on an electromechanical bicycle and palmar grip strength was measured using a Jamar dynamometer on day 1 and after 8 weeks. RESULTS IGF‐I increased significantly. Exercise capacity and maximum heart rate achieved on the electromechanical bicycle increased significantly. Grip strength did not change. There was a significant increase in fat‐free mass and a decline in fat mass as shown by dual energy X‐ray absorptiometry and bioelectrical impedance. However, this was not confirmed by other methods. No side‐effects were noted. CONCLUSIONS This study shows that a low dose of biosynthetic growth hormone can elevate IGF‐I levels and have a pronounced physical impact in the growth hormone deficient adult without the side‐effects seen at higher dosage schedules. Over a 2 month period the increase in fat‐free mass may be due to an increase in total body water; however, the decline in fat mass is a genuine effect.