Triiodothyronine serum levels decrease during controlled weight loss: an indicator of nutritional status in humans

Wednesday, October 26, 2011 — Poster Session III
10:00 a.m. – Noon	Natcher Conference Center	NIDDK	ENDOC-1

Authors

• R Agnihothri
• D Dellavalle
• JD Linderman
• S Smith
• A Courville
• S Yavuz
• L Simchowitz
• FS Celi

Abstract

Resting energy expenditure (REE) may account for up to 85% of total energy expenditure (EE). Thyroid hormone (TH) and particularly Triiodothyronine (T3) play a critical role in the modulation of REE. Limited information is available on the effects of prolonged weight loss on TH homeostasis. Aim of the study was the evaluation of the changes in TH in response to a controlled weight loss. 32 Control (19M, 13F, BMI 21.9±1.85,) and 47 Overweight Subjects (15M, 32F, BMI 34.12±4.56), age 25-45 were enrolled. Baseline procedures included: blood and urine sampling, anthropometry, and REE. Overweight Subjects underwent a one-year calorie-restricted diet (≈-600 Kcal/day). Study procedures were repeated at 1.5, 3, 6, 9, and 12 months. Baseline T3 levels correlated with BMI (p<0.02, R^2=0.074), and weight loss correlated with the decrease in T3 levels (p<0.0001, R^2=0.114). No significant correlation was observed between BMI and free T4, and between BMI and TSH levels. Our results indicate that T3 is a sensitive index of body weight changes, and that weight loss produces sustained changes in this parameter without affecting TSH or free T4. These data suggest that the peripheral conversion of the pro-hormone T4 into T3, its active metabolite, is affected by weight loss.

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