Background: Leptin is an adipocytokine that modulates metabolic processes, it reduces food intake & body adiposity and can improve insulin sensitivity. Hyperliptenaemia is a risk factor for coronary artery disease (CAD). Thyroid hormones play a major role in the maintenance of energy and lipid balance. Hypothyroidism is a common disorder that confers an increased cardiovascular risk. Also, prediabetes is associated with an increased risk of cardiovascular events. Clinical studies have demonstrated that adipocytokines play an important role in developing atherosclerotic cardiovascular diseases and that leptin may act as a mediator between obesity and CAD.
Aims: Assessment of the alteration of serum leptin in hypothyroid prediabetic patients and the relationship of this alteration to CAD risk factors.
Subjects and methods: 120 male patients were divided into 2 groups; Group A: 60 hypothyroid patients with normal glucose tolerance & Group B: 60 prediabetic hypothyroid patients. Group C: 60 healthy subjects. Complete clinical examination including waist circumference (WC) and blood pressure (BP). Fasting blood glucose (FBG), post prandial blood glucose (PPBG), basal serum cholesterol, triglycerides (TG), LDL, HDL, freeT3, freeT4, TSH, and fasting serum leptin level using ELISA assay were detected in all groups. 
Results: Compared to controls, patients in group A had; significantly higher serum leptin (mean 11.50±4.79 ng/ml Vs 3.83±1.36 ng/ml, p=0.0001), cholesterol (mean 191.92±73.33 mg/dl Vs 133.61± 32.45 mg/dl, p=0.0001), TG (mean 158.95±42.894 mg/dl Vs 120.14±25.06 mg/dl, p=0.0001), LDL (mean 132.92±59.34 mg/dl Vs 76.44± 32.38 mg/dl, p=0.0001), and lower serum HDL (mean 28.96±6.03 mg/dl Vs 36.51±3.49 mg/dl, p=0.001). In group B serum cholesterol, TG, and LDL were significantly higher than in group A. 
Conclusion: Serum leptin was significantly increased in hypothyroid patients with normal glucose tolerance and those with prediabetes. In all hypothyroid patients, leptin correlated positively with TSH, cholesterol, TG, LDL, and FBG, while it correlated negatively with FT3, FT4.

Study of serum leptin in prediabetic hypothyroid patients: relation to risk factors for coronary heart disease