Background and objectives: Our objective in this study was to discover the relationship of irisin hormone, which acts on adipose tissue and the metabolism as thyroid hormones, with the thyroid functions and the obesity secondary to thyroid disease.
Methods: A total of 74 patients were included in the study, of the patients, 37 were newly diagnosed with Hashimotos thyroiditis dependent hypothyroidism but not received a treatment yet, and the remaining 37 were healthy volunteers with no known disease. Serum TSH, free thyroxin (fT4), anti-thyroglobulin (anti-TG) and anti-thyroid peroxidase (anti-TPO) were measured and thyroid ultrasonography was performed to both group. The serum irisin levels were measured using the commercially available ELISA kit.
Results: The hypothyroidism group had higher levels of irisin compared with the control group (2.77 ng/ml vs 2.15 ng/ml respectively; P=0.017). The hypothyroidism group had higher median levels of irisin in the obese patients than those in the control group (3.10 ng/ml vs 2.10 ng/ml relatively; P=0.013). The irisin level was negatively correlated with the age in the entire population and patients with hypothyroidism (r: −0.255, P=0.028; r=−0.346, P=0.036 respectively). The irisin level was positively correlated with the TSH (r=0.247, P=0.034) but negatively with the fT4 (r=−0.316, P=0.006) in the entire population. Obesity, fT4 and irisin level were identified to be independent predictors in the diagnosis of hypothyroidism in the multivariable logistic regression analysis.
Conclusions: To the best our knowledge, this study is the first in literature to identify that obesity, irisin level and fT4 level are independent risk factors on hypothyroidism.