Evaluating the Effect of Hypothyroidism on Basal Metabolic Rate and Body Temperature Regulation

Background: Hypothyroidism is a clinical condition resulting from inadequate production of thyroid hormone, which is an important regulator of basal metabolic rate (BMR) and thermoregulation. Slow metabolism and altered thermogenesis experienced by hypothyroid patients may result in significant physiological disruption. This study aimed to evaluate the impact of hypothyroidism on body temperature regulation and BMR in adults with primary hypothyroidism. Methods: It was a cross-sectional analytical study conducted with 200 adults aged 25-50 years were enrolled, consisting of 100 hypothyroid patients and 100 age- and sex-matched healthy controls. The indirect calorimetry was used to measure the BMR, and the core body temperature was measured by digital thermometry in a controlled ambient condition. The chemiluminescent immunoassay was used to measure thyroid function, including thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4). Independent t-test was used to measure continuous variables, and chi-square test for categorical variables through SPSS. p < 0.05 was considered statistically significant. Results: The hypothyroid group demonstrated lower BMR compared to controls (1195.8 ± 105.4 kcal/day vs. 1362.7 ± 112.3 kcal/day; p < 0.001). A decrease in core body temperature was also observed (p < 0.001). There was a significant alteration in thyroid hormone levels with increased TSH (9.22 ± 2.1 IU/mL) and decreased free T3 (2.12 ± 0.5 pg/mL) and T4 (0.62 ± 0.2 ng/dL) in the hypothyroid group (all p < 0.001). Conclusion: Hypothyroidism significantly diminishes metabolism rate and affects thermoregulation, highlighting that diagnosis and intervention are necessary.