No association between zinc and thyroid activity in obese women.

Abstract

Obesity is characterized by changes in the metabolism of zinc and thyroid hormones. Studies have also shown the role of zinc in the function and metabolism of thyroid. The present study aimed to evaluate the relationship between serum concentrations of thyroid hormones, dietary zinc intake and zinc distribution in obese women. A case-control study was conducted enrolling 98 women aged between 20 and 50years old who were divided into case group (BMI≥35kg/m2) and control group (BMI=18.5-24.9kg/m2). Patients underwent anthropometric measurements and analysis of dietary zinc intake, which was performed by a three-day food record. Zinc concentrations in plasma and erythrocytes were determined by inductively coupled plasma optical emission spectrometry. Serum concentrations of thyroid hormones and antibodies were determined by chemiluminescence. Mean values of dietary zinc intake were higher than recommended (10.37±3.12mg/day and 11.37±4.36mg/day for control and obeses, respectively). Obese women had reduced plasma (67.22±5.96μg/dL) and erythrocyte (37.16±3.64μg Zn/gHb) zinc concentrations when compared to the control group (plasma: 89.71±13.33μg/dL; erythrocyte: 42.68±3.73μg Zn/gHb) (p<0.001). Serum TSH (control: 2.62±1.29 μIU/mL; obeses: 3.08±1.13 μIU/mL), Free T3 (control: 2.19±0.63pg/dL; obeses: 2.09±0.34pg/dL), and Free T4 (control: 1.12±0.31ng/dL; obeses: 1.09±0.19ng/dL) concentrations were within the normal range in both groups, without significant difference between them (p>0.05). There was no correlation between thyroid hormone concentrations and zinc parameters (p>0.05). Although obese women presented hypozincemia, they had normal levels of thyroid hormones and no correlation was found between the studied parameters.