Endocrine Abstracts

Background: Thyroid volume correlates positively with body mass index (BMI). This correlation holds true for both iodine-sufficient and mild/moderate iodine-deficient areas. We examined the association between thyroid volume and BMI and change in BMI over 4 years in middle-age adults recruited from the general population.

Methods: A total of 2495 subjects, for whom thyroid volume, FT₄ and TSH were available (women aged 35–60 years and men aged 45–60 years), were derived from the Supplementation en Vitamines et Mineraux Antioxydants (SU.VI. MAX) cohort study conducted in France since baseline (1994). Weight and height were measured 2 and 6 years after inclusion. Linear univariate and multiple regression analyses were performed to evaluate correlations between thyroid volume and BMI at 2 and 6 years and BMI change from year 2 to 6.

Results: Baseline thyroid volume was positively correlated with BMI at 2 years (men: β=0.09, P<0.01; women: β=0.09, P<0.01) and 6 years after inclusion (men: β=0.10, P<0.01; women: β=0.09, P<0.01). The correlation between thyroid volume and BMI at 2 and 6 years remained significant after adjusting for free T₄, TSH, gender, age, smoking, alcohol consumption and TSH-thyroid volume interaction factor (β=0.11, P<0.01). Baseline thyroid volume was not correlated with BMI change from year 2 to 6 in linear regression analysis.

Conclusion: In French adults, thyroid volume predicted BMI at 2 and 6 years. This association may be explained by the observation that leptin stimulates biosynthesis of TRH in vitro.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.