Adipose tissue secreted hormonal mediators, adipokines play pivotal roles in the regulation of, among others, central nervous and immune systems influencing body weight, insulin action and inflammatory responses. The aim of our present study was to investigate possible associations of thyroid function with plasma levels of three of known adipokines, i.e. leptin, adiponectin and resistin in 74 Caucasian subjects without any endocrine diseases or related therapy. In order to create broad adipokine ranges, 3 age-, and sex-matched groups were formed: Group 1 and 2 consisted of non-diabetic obese patients (n=25 with BMI: 2839.9 kg/m2, n=25 with BMI ≥40 kg/m2, respectively), while Group 3 of 24 healthy, normal weight control subjects. Level of TSH was correlated negatively with leptin (r=−0.26, P<0.05), while positively with adiponectin (r=0.28, P<0.05). Both were independent predictors of TSH level in a multiple regression model including BMI, age, gender, FT3 or FT4. But when both leptin and adiponectin were included into the model, only the latter remained significant. In opposite to TSH, level of FT3 was negatively associated with adiponectin (r=−0.27, P<0.05) and showed a positive trend with leptin (r=0.26, P=0.06) of which the latter was independent predictor in multivariate analyses, beside age, BMI and FT4. FT4 was not correlated with any of adipokines. In univariate analysis, neither BMI, nor resistin was significantly correlated with thyroid function parameters.
In conclusion, in individuals without thyroid illness, leptin and adiponectin plasma levels are associated with TSH and FT3 concentrations in opposite ways, and partly independently of anthropometric parameters. Adipokines may participate in the regulation of thyroid hormone axis.