Can we consider a lower cutoff value for diagnosis of subclinical hypothyroidism in patients with obesity based on leptin levels?

Background Thyroid hormones play a major role in thermogenesis, lipid, and glucose metabolism. Previous studies suggested that minor laboratory differences in thyroid function tests, within reference range, can contribute to increased incidence of weight gain. So, we aimed to investigate the possibility of a lower cutoff value of subclinical hypothyroidism in patients with obesity based on leptin levels to start treatment earlier and prevent further weight gain. Results Upon analysis of data from two groups obese (55 patients) and nonobese (35 patients) for whom serum leptin and thyroid-stimulating hormone (TSH) were measured to assess the relation between serum leptin and TSH levels in obese patients, the mean TSH level (mIU/l) of the obese group was 4.13±2.44, whereas in the control nonobese group was 2.32±1.19, and the mean leptin level (ng/ml) of the obese group was 47.25±28.03, whereas in the nonobese group was 4.90±3.13. The receiver operating characteristic curve showed that the diagnostic cutoff point for TSH was 4.09, with sensitivity of 41.8% and specificity of 88.6%, whereas the diagnostic cutoff point for leptin was 12.75, with sensitivity of 98.2% and specificity of 97.1%. Conclusions The results of the study showed that TSH levels more than 4.09 mIU/l can be considered diagnostic of subclinical hypothyroidism in obese people, similar to other population, apart from pregnant women. So, based on leptin levels, a lower cutoff value of TSH cannot be considered diagnostic of subclinical hypothyroidism in obese population.