[01] Maher K. Ibrahim, Department of Biochemistry, College of Medicine, University of Tikrit, Tikrit, Iraq. [02] Abdul-Monaim H. Al-Samarrai, Department of Chemistry, College of Education, University of Samarra, Samarra, Iraq. [03] Khudhair A. Khudhair, Department of Biochemistry, College of Medicine, University of Tikrit, Tikrit, Iraq.

Leptin is a hormone secreted by adipose tissues and is considered as a satiety hormone, it is known to be an important regulator of food intake and energy storage. Disturbance of thyroid function is associated with marked changes in both body weight and energy expenditure, and it has therefore been the subject of much research to study the mutual roles of leptin and thyroid hormones in this respect. Very few researches are done to investigate the possible association of serum leptin and thyroid hormones in Iraq. Despite intensive research in this field, results are still not very clear. Objective of this study was to find any possible association of serum leptin levels and thyroid hormones. This prospective, randomized study was conducted in Baghdad; Iraq. The subjects were selected from Medical City Hospital. Serum samples were collected from 180 individuals; 56 (31%) of them were males and 124 (69%) females. The patients classified into three groups, two groups for thyroid dysfunctions patients (hypothyroid and hyperthyroid patients) and the third group as control group (euthyroid). The body weight of each individual was measured using a carefully calibrated weighing balance. The height of each individual was measured to calculate BMI ratio. Blood samples were taken early in the morning, 12 hours postprandial. The serum samples were stored at (20C) until required for thyroid hormones (Total and Free T3, T4 & TSH) and plasma leptin measurements (by using ELISA). To determine if serum leptin levels are affected by thyroid dysfunction, we measured its concentration in serum samples from 55 euthyroid controls, mean age 36.9±9.9 yr and 125 subjects: 74 patients with hypothyroidism, mean age 44.3±7.0 yr, and 51 patients with hyperthyroidism, mean age 43.5±6.9 yr. Mean leptin levels in the euthyroid (3.69±1.94 ng/ml), hypothyroid (4.97±2.61 ng/ml) and hyperthyroid (2.36±1.26 ng/ml) groups were significantly different. The results showed no significant correlation in serum leptin and T3, T4, FT3, FT4, TSH either in the hypothyroid or in the hyperthyroid and euthyroid control group of patients. These data suggest that leptin levels are not affected by thyroid dysfunction. There was a significant positive correlation between BMI and leptin level (r = 0.29, p =.03) in euthyroid controls, (r = 0.35, p =.01) in hypothyroid and (r = 0.33, p =.01) in hyperthyroid. Serum leptin levels in males were lower than those recorded in females [hypothyroid patients; 4.4±2.1 and 5.1±2.7 ng/ml; P˃0.05: hyperthyroid patients; 2.0±0.63 and 2.5±1.45 ng/ml; P˃0.05: euthyroid; 3.2±1.8 and 3.9±2.0 ng/ml; P˃0.05]. In conclusion, leptin hormone was no significantly correlated with thyroid hormone function in eu-, hypo-, and hyperthyroid patients. Leptin level is highly correlation with the BMI might be confirmed that BMI and gender are the major determinant of leptin levels.

Leptin, Hyperthyroidism, Hypothyroidism, Euthyroidism

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