The thyroid hormones are important for regulating weight. It is well known that hypothyroidism (an underactive thyroid gland) can lead to slower metabolism, weight gain and a higher body-mass index. Subclinical hypothyroidism (SCH) is one of the most common endocrine disorder which varies worldwide and has been most frequently found in women rather than males. In India, its prevalence varies from 9% to 12%. Thyroid hormones lead to increase basal metabolic rate in the body by inducing metabolic activities in most tissues. Frequent Increase in weight can be the cause of various diseases and also lead to obesity, which can affect the metabolism of the body. Several other diseases, e.g., cardiovascular risk, diabetes, etc. associated with obesity may be developed in later years. Hence the present study was planned for Association of the TSH Level and Its Relation to Body Weight in Patients from Bihar Region. The present study was planned in Department of General Medicine, Patna Medical College and Hospital, Patna, Bihar, India. Total 50 cases of the patients undergone screening for thyroid illness were enrolled in the present study. The age, height, and weight of the individuals were noted and the body mass index (BMI) was calculated in all the individuals. The serum TSH levels were measured using ECLIA method. The data generated from the present study concludes that variations of TSH are accompanied by differences in BMI perhaps due to the changes in the basal metabolic rate. The high incidence of the pathological disorders in thyroid function with associated various environmental factors (diet, exercise, etc.) cause weight gain with an unknown biological mechanism and lead to obesity.