The role of leptin resistance in the development of thyroid neoplasia

Abstract

Background. Leptin influences energy metabolism, as it is able to inform the central nervous system about adipose tissue reserves, and is also an important neuroendocrine regulator. Therefore, an increase in leptin stimulates thyrotropin-releasing hormone secretion, which leads to an increase of thyroid-stimula­ting hormone with normal or slightly elevated levels of thyroxine and triiodothyronine. Leptin imbalance leads to leptin resistance, which develops as a result of impaired sensitivity of hypothalamic receptors to leptin, its penetration through the blood-brain barrier, damage or dysfunction of these receptors, dysfunction of transport proteins accompanied by an increased content of inflammatory mediators that affect leptin receptors and, in turn, damage them. The purpose of the study was to reveal the relationship between hyperleptinemia and leptin resistance in people with different body weight and thyroid nodules. Materials and methods. One hundred and twenty-three patients were examined, who were divided into four groups depen­ding on the body mass index to determine the le­vels of leptin, insulin, and degree of insulin resistance: group 1 — excess body weight (n = 22); group 2 — class 1 obesity (n = 28); group 3 — class 2 obesity (n = 32); group 4 — class 3 obesity (n = 21). The control group consisted of persons with normal body weight (n = 20). Results. It was found that all examined patients had hyperleptinemia (34.5 ng/ml) simultaneously with hyperinsulinemia and insulin resistance (HOMA-IR was 8.3 units). Patients with thyroid neoplasia compared to individuals with normal body weight had significantly higher (by 1.3 times) serum leptin concentrations (p < 0.05; p < 0.001). The research proved that the level of leptine­mia is directly related to the body mass index, waist circumference (r = 0.54; p < 0.001) and hip circumference (r = 0.51; p < 0.001). Conclusions. Among patients with leptin resistance and insulin resistance against the background of obesity of various classes, thyroid neoplasms occur in 28 % of cases. Leptin resistance along with insulin resistance can be considered as independent risk factor for neoplasia. People with abdominal obesity need a mandatory exami­nation of the structural and functional state of the thyroid gland for early detection of nodular neoplasms.