Free T3/Free T4 Ratio Linked to Metabolic Syndrome

Nelson Vergel

Founder, ExcelMale.com
Free Triiodothyronine/Free Thyroxine Ratio rather than Thyrotropin is more associated with Metabolic Parameters in Healthy Euthyroid Adult Subjects.

Park SY, et al. Clin Endocrinol (Oxf). 2017.


Abstract
OBJECTIVE: The interrelation between TSH, thyroid hormones, and metabolic parameters is complex and has not been confirmed. This study aimed to determine the association of TSH and thyroid hormones in euthyroid subjects and the relationship between thyroid function and metabolic risk factors. Furthermore, this study examined whether thyroid function has predictive power for metabolic syndrome.

DESIGN: This is a cross-sectional study that included subjects in a medical health check-up program at a single institution.

PATIENTS: The study included 132,346 participants (66,991 men and 65,355 women) aged over 18 years who had TSH, free T4 (FT4), and free T3 (FT3) levels within the institutional reference ranges.

MEASUREMENTS: TSH, FT4, FT3, and metabolic parameters including height, weight, waist circumference, blood pressure, serum levels of total cholesterol, triglyceride, high-density lipoprotein cholesterol, insulin, and glucose were measured.

RESULTS: There was a positive association between FT3/FT4 ratio and TSH in both men and women after adjusting for age, body mass index, smoking status, and menopausal status (in women). The FT3/FT4 ratio and TSH were positively associated with risk of metabolic syndrome parameters including insulin resistance. The FT3/FT4 ratio had a greater predictive power than TSH for metabolic syndrome in both men and women.

CONCLUSIONS: TSH levels were positively associated with FT3/FT4 ratio within the euthyroid range. The higher FT3/FT4 ratio is associated with increased risk of metabolic syndrome parameters and insulin resistance. FT3/FT4 ratio has a better predictive power for metabolic syndrome than TSH. This article is protected by copyright. All rights reserved.
 

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Scientific Reference

Lakshman KM, Kaplan B, Travison TG, Basaria S, Knapp PE, Singh AB, LaValley MP, Mazer NA, Bhasin S. The effects of injected testosterone dose and age on the conversion of testosterone to estradiol and dihydrotestosterone in young and older men. J Clin Endocrinol Metab. 2010 Aug;95(8):3955-64.

DOI: 10.1210/jc.2010-0102 | PMID: 20534765 | PMCID: PMC2913038

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