Effects of depot growth hormone replacement on thyroid function and volume in adults with congenital isolated growth hormone deficiency

Background: Conflicting data exist on the effects of GH replacement therapy (GHRT) on thyroid function and thyroid volume (TV) in GH-deficient (GHD) patients. Aim: The aim of this study was to assess the effects of GHRT on thyroid function and TV in adults with congenital lifetime isolated GHD (IGHD). Subjects and methods: We studied 20 GH-naive adults with IGHD due to a homozygous mutation of the GHRH-receptor gene at baseline, after 6-month depot-GH replacement therapy (pGH), and 6-month washout (6mo). Total T-3, free T-4 (FT4), reverse T-3 (rT(3)), TSH, IGF-I, SHBG, and TV were measured; body surface area-corrected TV (CTV) was calculated. Results: IGF-I and T-3 increased pGH. T-3 levels remained elevated at 6mo. GHRT did not significantly change FT4, rT(3), TSH, and SHBG. TV and CTV increased pGH and remained elevated at 6mo. Conclusions: GHRT in IGHD adults caused an increase in serum T-3 levels and TV, suggesting an important role of the GH-IGF-I axis in thyroid function. (J. Endocrinol. Invest. 35: 265-268, 2012) (C) 2012, Editrice Kurtis