Partial substitution of Thyroxine (T4) with Tri-Iodothyronine in patients on T4Replacement therapy: results of a large community-based randomized controlled trial

Saravanan, Ponnusamy, Simmons, Dawn J., Greenwood, Rosemary, Peters, Tim J. and Dayan, Colin Mark ORCID: https://orcid.org/0000-0002-6557-3462 2005. Partial substitution of Thyroxine (T4) with Tri-Iodothyronine in patients on T4Replacement therapy: results of a large community-based randomized controlled trial. Journal of Clinical Endocrinology & Metabolism 90 (2) , pp. 805-812. 10.1210/jc.2004-1672

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Abstract

Conflicting results have recently been published about the benefits of combined T4 and T3 in treating hypothyroid patients. However, these studies may have been underpowered to detect differences in psychological well-being specifically related to T4 replacement. We conducted a large, double-blind, randomized controlled trial of partial substitution of 50 μg T4 by 10 μg T3 vs. the original dose of T4 in 697 hypothyroid patients. Thyroid function showed a rise in TSH (132%), a fall in free T4 (35%, P < 0.001), and unchanged basal free T3 levels (P = 0.92). At 3 months, there was a large (39%) placebo effect improvement in psychiatric caseness defined by the General Health Questionnaire (GHQ) 12 score in the control group compared with baseline, and this was sustained at 12 months. Differences vs. the intervention (T3) group were more modest with improvements in GHQ caseness (odds ratio, 0.61; 95% confidence interval, 0.42, 0.90; P = 0.01) and Hospital Anxiety and Depression questionnaire-anxiety scores at 3 months (P < 0.03) but not GHQ Likert scores, Hospital Anxiety and Depression questionnaire-depression, thyroid symptoms, or visual analog scales of mood and the initial differences were lost at 12 months. These results may be consistent with a subgroup of patients showing transient improvement after partial substitution with T3 but do not provide conclusive evidence of specific benefit from partial substitution of T4 by T3 in patients on T4 replacement. They also emphasize the large and sustained placebo effect that can follow changes in thyroid hormone administration.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine Systems Immunity Research Institute (SIURI)
Subjects:	R Medicine > R Medicine (General)
Publisher:	The Endocrine Society
ISSN:	0021-972X
Last Modified:	27 Oct 2022 08:53
URI:	https://orca.cardiff.ac.uk/id/eprint/63705

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