Growth hormone replacement improves thyroxine biological effects: Implications for management of central hypothyroidism

Growth hormone replacement improves thyroxine biological effects: Implications for management of central hypothyroidism

Author Martins, Manoel Ricardo Alves Autor UNIFESP Google Scholar
Doin, Fabio Luiz Casanova Autor UNIFESP Google Scholar
Komatsu, William Ricardo Autor UNIFESP Google Scholar
Barros Neto, Turibio Leite de Autor UNIFESP Google Scholar
Moisés, Valdir Ambrósio Autor UNIFESP Google Scholar
Abucham, Julio Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract Context: the biological significance of GH-induced changes in serum TH concentrations is unknown. It has been suggested that serum free T(4) (FT(4)) should be targeted at the high-normal range during GH replacement.Objective: Our objective was to evaluate the effects of GH replacement on T4 biological effects.Hypothesis: If GH modulates thyroxine biological effects, serum FT(4) should be targeted accordingly.Design and Setting: We conducted observational ( study 1) and interventional ( studies 2 and 3)/outpatient studies.Patients: Thirty-two GH-deficient patients ( 13 off GH; 22 on L-T(4)) participated in the study.Interventions: in study 2, levothyroxine was administered to increase FT(4) (> 1.0 ng/dl). in study 3, GH was administered or withdrawn.Main Outcome Measures: We measured FT(4), total T(3) (TT(3)), myocardial isovolumic contraction time (ICT), and resting energy expenditureResults: in study 1, off-GH and on-GH groups had similar FT(4), but off GH showed lower TT(3) ( P < 0.01) and REE ( P = 0.02), higher ICT ( P < 0.05) than on-GH and controls. On GH, ICT and REE correlated only with TT(3) ( r = -0.48; r = 0.58; P < 0.05). Off GH, ICT correlated only with FT(4) ( P = 0.01). in study 2, off GH, levothyroxine intervention increased FT(4) ( P = 0.005) and TT(3) ( P = 0.012), decreased ICT ( P = 0.006), and increased REE ( P = 0.013); ICT and FT(4) changes correlated ( r = -0.72; P = 0.06). On GH, levothyroxine increased FT(4) ( P = 0.0002), TT(3) ( P = 0.014), and REE ( P = 0.10) and decreased ICT ( P = 0.049); REE and TT(3) changes correlated ( r = 0.60; P = 0.05). in study 3, GH decreased FT(4), increased TT(3), decreased ICT, and increased REE ( P < 0.05). REE correlated ( P < 0.05) with IGF-I ( r = 0.57) and TT(3) ( r = 0.64). ICT correlated only with TT(3) ( r = -0.46).Conclusions: GH replacement improves the biological effects of T4. Serum FT(4) should be targeted at the high-normal range in GH-deficient patients only off GH replacement.
Language English
Date 2007-11-01
Published in Journal of Clinical Endocrinology & Metabolism. Chevy Chase: Endocrine Soc, v. 92, n. 11, p. 4144-4153, 2007.
ISSN 0021-972X (Sherpa/Romeo, impact factor)
Publisher Endocrine Soc
Extent 4144-4153
Origin http://dx.doi.org/10.1210/jc.2007-0941
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000250763800012
URI http://repositorio.unifesp.br/handle/11600/30108

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