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Body mass and serum thyrotropin are not associated in euthyroid patients with thyroid disorders

(March 2006)

The background of the study. Thyroid function within the normal range may be a determinant of body weight. In this study, the relationships between serum thyrotropin (TSH) and free thyroxine (T4) concentrations and body-mass index were determined in patients with thyroid disorders who had normal thyroid function.

How the study was done. The study subjects were 401 patients referred to a thyroid clinic in the United Kingdom for evaluation of a thyroid nodule or goiter. Weight, height, and serum TSH and free T4 were measured. Twenty-seven patients (7 percent) proved to have thyroid carcinoma.

The results of the study. There was no correlation between body-mass index and serum TSH concentration or serum free T4 concentration in the 401 patients, or in the women or men separately. The median body-mass index values were similar in subgroups of the patients formed according to tertiles of serum TSH or serum free T4. The median serum TSH and free T4 concentrations also were similar in the patients whose body-mass index was ≥30 kg/m2 (obese) and those with a body-mass index <30 kg/m2 (nonobese). There was no correlation between either serum TSH or free T4 and body-mass index in the obese group. Exclusion of the 27 patients with thyroid carcinoma did not alter the results.

The conclusions of the study. Serum TSH and free T4 concentrations are not associated with body-mass index in patients with thyroid nodules or goiter who have normal thyroid function.

The original article. Manji N, Boelaert K, Sheppard MC, Holder RL, Gough SC, Franklyn JA. Lack of association between serum TSH or free T4 and body mass index in euthyroid subjects. Clin Endocrinol (Oxf) 2006;64:125-8.