Resistin levels are normal in hypothyroidism and remain unchanged after attainment of euthyroidism: Relationship with insulin levels and anthropometric parameters

The aim of this controlled prospective study was to investigate resistin levels in hypothyroidism before and after restoration of euthyroidism and correlate the results with body weight (BW), body fat (BF), waist circumference (WC), body mass index (BMI) and serum insulin levels. Fifty-three hypothyroid patients with Hashimoto's disease (6 males, 47 females) and 30 controls matched for age, BMI and BF were investigated. Anthropometric parameters, resistin and insulin levels were measured. All patients were started on levothyroxine treatment and 4 to 5 months after initiation of treatment the investigations were repeated. Hypothyroid patients exhibited normal resistin values, which were no different from controls (mean SD 7.4 +/- 4.0 vs 5.1 +/- 3.5 ng/ml, p=0.063). Normalization of circulating thyroid hormone levels produced no significant change in resistin levels (7.4 +/- 4.0 vs 6.8 +/- 4.2 ng/ml, p=ns) and post-treatment resistin levels did not differ from euthyroid controls. Furthermore, no gender difference was demonstrated in resistin levels either before (6.4 +/- 3.7 for males vs 7.6 +/- 4.1 ng/ml for females, p=ns) or after therapy (7.9 +/- 4.3 vs 6.7 +/- 4.3 ng/ml, for males and females respectively, p=ns), nor was there a difference in resistin levels in either sex induced by treatment of hypothyroidism (6.4 3.7 vs 7.9 4.3 ng/ml for males, p=ns, and 7.6 4.1 vs 6.7 4.3 ng/ml for females, p=ns). However, a small but significant difference in resistin levels was found between female patients and female controls (7.6 4.1 vs 5.0 +/- 4.0 ng/ml, p=0.047). Insulin levels and homeostasis model assessment insulin resistance (HOMA-IR) index did not differ before and after treatment in hypothyroid patients (13.0 +/- 10.2 vs 12.6 +/- 11.8 mu U/ml, 22.7 +/- 1.4 vs 21.8 +/- 1.3, respectively, p=ns for both) or between patients and controls. In conclusion, our results demonstrate that resistin levels are normal in hypothyroidism and remain within normal range after attainment of euthyroidism. Resistin is not associated with serum insulin and HOMA-IR index, as well as BMI, BF, WC and BW.