Effects of growth hormone administration on fuel oxidation and thyroid function in normal man.
In a randomized, double-blind, placebo-controlled, cross-over study, we examined the effects of 14 days of growth hormone (GH) administration (12 IU/d subcutaneously) on energy expenditure (EE), respiratory exchange ratio (RER), and thyroid function in 14 normal adults of normal weight (eight men and six women). EE (kcal/24 h) was significantly elevated after GH administration (2,073 +/- 392, [GH], 1,900 +/- 310, [placebo], P = .01). RER was significantly lowered during GH administration (0.73 +/- 0.04 v 0.78 +/- 0.06, P = .02), reflecting increased oxidation of lipids. Total triiodothyronine (TT3) (nmol/L) and free T3 (FT3) (pmol/L) increased significantly during GH (TT3: 1.73 +/- 0.06 [GH], 1.48 +/- 0.08 [placebo], P = .01; FT3: 6.19 +/- 0.56 [GH], 5.49 +/- 0.56 [placebo], P = .01). Concomitantly, an insignificant decrease in reverse T3 (rT3) (nmol/L) was observed (0.07 +/- 0.01 [GH], 0.15 +/- 0.01 [placebo], P = .08). GH caused a highly significant increase in T3/thyroxine (T4) (x 100) ratio (1.84 +/- 0.12 [GH], 1.37 +/- 0.06 [placebo]). Serum thyrotropin (TSH) was not significantly changed by GH. No changes in total thyroxine (TT4) (nmol/L) (98 +/- 6 [GH], 111 +/- 8 [placebo], P = .40) and free thyroxine (FT4) (pmol/L) (17.4 +/- 1.3 [GH], 18.6 +/- 1.1 [placebo], P = .37) after 14 days of GH administration were observed. In conclusion, 2 weeks of GH administration increases EE and lipidoxidation. This finding may partly be mediated by an increase in peripheral T4 to T3 conversion.
Møller
J
J
University Department of Internal Medicine and Endocrinology, Aarhus Kommunehospital, Denmark.
Jørgensen
J O
JO
Møller
N
N
Christiansen
J S
JS
Weeke
J
J
D000328:Adult; D004734:Energy Metabolism / Q000187:drug effects*; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000502:physiology; D008297:Male; D010084:Oxidation-Reduction; D013961:Thyroid Gland / Q000187:drug effects* / Q000502:physiology; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood
D013963:Thyroid Hormones; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D013006:Growth Hormone