Triiodothyronine administration reduces serum growth hormone levels and growth hormone responses to thyrotropin-releasing hormone in patients with anorexia nervosa.
The aim of this study was to test the hypothesis that low serum T3 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 T3 circulating levels (mean +/- SEM = 2.8 +/- 0.3 pmol/l) were studied. A TRH test (200 micrograms IV) was carried out under basal conditions and repeated following treatment with oral T3 (1.5 micrograms/kg BW/day) for eight days. Following T3 administration, GH levels dropped significantly from a baseline of 7.1 +/- 1.3 micrograms/l to 3.1 +/- 0.7 micrograms/l (p less than 0.02), as did GH peak responses to TRH (9.0 +/- 1.0 micrograms/l vs 4.4 +/- 0.8 micrograms/l, p less than 0.01). ANOVA and analysis of area under the curve (AUC) confirmed that after T3 treatment there was a significant reduction in TRH-induced GH release in these patients (GH AUC: 902 +/- 132 micrograms/l vs. 456 +/- 91 micrograms/l, p less than 0.02). TSH responses to TRH, which were normal prior to T3 treatment, completely disappeared following it, and PRL responses to TRH also were diminished. Although our experimental approach does not permit a conclusion that low T3 levels were the primary reason for these changes, the data support the theory that low T3 circulating levels may facilitate abnormal GH secretion and the GH-releasing activity of intravenous TRH.
Valcavi
R
R
2a Divisione Medicina Generale, Arcispedale S. Maria Nuova, Reggio Emilia, Italy.
Zini
M
M
Portioli
I
I
D000293:Adolescent; D000328:Adult; D000856:Anorexia Nervosa / Q000097:blood*; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D011388:Prolactin / Q000097:blood; D012016:Reference Values; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone; D014284:Triiodothyronine / Q000008:administration & dosage*; D014285:Triiodothyronine, Reverse / Q000097:blood
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013973:Thyrotropin-Releasing Hormone; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone