Abstract
The aim of this study was to test the hypothesis that low serum T 3 concentrations may promote an abnormal growth hormone (GH) response to thyrotropin-releasing hormone (TRH) in patients with anorexia nervosa. Eight anorexic women and two anorexic men, ages 15–25 years, with low free T 3 circulating levels (mean ± SEM = 2.8 ± 0.3 pmol/l) were studied. A TRH test (200 μg IV) was carried out under basal conditions and repeated following treatment with oral T 3 (1.5 μg/kg BW/day) for eight days. Following T 3 administration, GH levels dropped significantly from a baseline of 7.1 ± 1.3 μg/l to 3.1 ± 0.7 μg/l ( p<0.02), as did GH peak responses to TRH (9.0±1.0 μg/l vs. 4.4 ± 0.8 μg/l, p<0.01). ANOVA and analysis of area under the curve (AUC) confirmed that after T 3 treatment there was a significant reduction in TRH-induced GH release in these patients (GH AUC: 902±132 μg/l vs. 456±91 μg/l, p<0.02). TSH responses to TRH, which were normal prior to T 3 treatment, completely disappeared following it, and PRL responses to TRH also were diminished. Although our experimental approach does not permit a conclusion that low T 3 levels were the primary reason for these changes, the data support the theory that low T 3 circulating levels may facilitate abnormal GH secretion and the GH-releasing activity of intravenous TRH.
Published Version
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