ABSTRACT
Leptin is an adipocyte-secreted protein, which functions as a metabolic, neuroendocrine hormone beside its role in regulation of food intake and energy balance. The aim of this study was to assess the influence of hypo and hyperthyroidism on plasma leptin levels. Also, we studied some biochemical changes and its relation to serum leptin. This study was done on patients with newly discovered thyroid disorders [17 cases with hypothyroidism and 19 cases with hyperthyroidism] and 19 lean euthyroid subjects as a control group. We measured the plasma leptin levels, thyroid hormones, and different biochemical variables "serum calcium [Ca], phosphorus [P], alkaline phosphatase [ALP], uric acid, serum urea, creatinine, and complete lipogram and their relation to plasma leptin. The mean leptin levels were higher in hypothyroid patients [9.5 ng/ml in males and 11.9 ng/ml in females] and lower in hyperthyroid patients [1.2 ng/ml in males and 2.8 ng/ml in females] compared with controls [2.4 ng/ml in male and 6.6 ng/ml in female]. Leptin was significantly negatively correlated with thyroxine [T[4]] [r = -0.74 P < 0.0001], triiodothyronine [T[3]] [r = -0.57,]P <0.005] and positively correlated with thyroid stimulating hormone [TSH] [r = 0.78 P <0.0001] after adjusting for body mass index [BMI] and Lipids, Also, plasma leptin significantly positively correlated with BMI = [r = 0.45, P < 0.005]. No significant correlation was observed between plasma leptin and lipids after adjusting for BM1 and thyroid hormones. Their was no significant correlation between leptin and Ca,k ALP, P, uric acid or creatinine. Plasma leptin was significantly elevated in hypothyroidism and decreased in hyperthyroidism, compared with controls. T[4], T[3] and TSH area potent regulator of plasma leptin independent of BMI