Association of Serum Thyroid Hormones and Serum Leptin with Body Mass Index

Leptin is a hormone secreted by adipose tissues and is considered as a satiety hormone, which inhibits feeding. Much research is being carried out internationally to understand role of leptin in obesity and related disorders. Thyroid hormones are important in metabolism and energy expenditure. Very few researches are done to investigate the possible association of serum leptin and thyroid hormones with body mass index in Pakistan. Objective of this study was to find any possible association of serum leptin levels and thyroid hormones, namely, thyroxine (T 4 ), triiodothyronine (T 3 ) and thyroid stimulating hormones (TSH) with body mass index (BMI). This prospective, randomized study was conducted in Lahore, Pakistan. The subjects were selected from Outpatient Department of Internal Medicine, Mayo Hospital and British Sliming Center. The consent from the patients was taken before their participation in this study. The subjects were classified into two categories; obese (BMI>30) and Non-Obese (BMI<25). The nutritional status of all subjects was assessed by means of anthropometric measurements. The body weight of each individual dressed in light clothing was measured using a carefully calibrated weighing balance. The height of each individual was measured using a vertical-measuring rod; a waist and hip circumference was also measured to calculate waist/hip ratio. Blood samples were taken early in the morning, 12 hours postprandial. About 10 ml of venous blood was drawn from the subjects. The serum samples were stored at 2-5°C for not more than 24 hours prior to Thyroid hormones (T 3 , T 4 & TSH) and plasma Leptin measurements. Serum T 3, T4, TSH and Leptin concentration was measured by using ELISA. Data was processed and analyzed using the Statistical Package for the Social Sciences (SPSS) version 16. The mean age of the patients was 45.35 ± 5.96 years with minimum and maximum age 32-58 years respectively. Total 91 subjects were selected. 43 (47.3%) of them were males and 48 (52.7 %) females. The results showed positive significant correlation in BMI and Serum Leptin, r=0.316 (0.002), BMI and Thyroxine (T4), r= 0.113 (0.008), BMI and Tri-iodothyronine (T3), r= 0.171 (0.017) and BMI and Thyroid stimulating hormone (TSH), r= 0.276 (0.000). These results suggest that there is a relationship between plasma leptin levels and thyroid hormones. Based on the results of this study it can be concluded that there exists some relationship between thyroid hormones and plasma leptin. Further studies must be carried out to further investigate how leptin interacts with thyroid hormones and vice versa.