Endocrine Abstracts

Background and aim

The epidemic of overweight and obesity presents a major challenge to chronic disease prevention and health across the life course around the world. The putative relationships between thyroid hormones, body weight, and adipose tissue homeostasis have been the focus of several studies in recent years, but the causal relationships between these parameters have not been well established. Aim of the study: to investigate the relationship between serum thyroid stimulating hormone (TSH), insulin resistance (IR), and cardiovascular risk factors in a sample of obese persons with subclinical hypothyroidism.

Materials and methods

A retrospective, longitudinal analysis of 145 obese persons was performed. The TSH and free thyroxine (fT₄) levels, anthropometric measurements, and laboratory test results were analyzed. Euthyroid patients were also divided into two groups according to TSH levels. There has been some discussion about lowering the upper value of TSH to 2.5 µIU/ml. This discussion is based in some data that indicated that patients with TSH ≥ 2.5 may have different profiles than those with TSH < 2.5 µIU/ml

Results

35 individuals presented with TSH levels above the normal level (subclinical hypothyroidism). Their waist circumference (WC) was significantly higher than those of euthyroid individuals. Serum TSH was positively correlated with the homeostasis model assessment of insulin resistance (HOMA-IR) index, triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C). Using TSH and BMI as independent variables, TSH levels were shown to be independently related to HOMA-IR (P = 0.002) and triglycerides (P = 0.006). Among euthyroid subjects, individuals with TSH values <2.5 mIU/ml exhibited statistically significant decreases in waist-to-hip ratio, HDL-C levels, and HOMA-IR scores and a tendency toward lower WC values.

Conclusion

Subclinical hypothyroidism in overweight and obese persons appears to be associated with excess weight, especially visceral weight. In the present sample of obese persons, TSH levels appear to be associated with insulin resistance.

Keywords

subclinical hypothyroidism, obesity, cardiovascular risk factors.