Short-Term Weight Changes in Treated Primary Hypothyroid Subjects

Weight loss due to diuresis is an early clinical response of treatment with levothyroxine in primary hypothyroidism. The objective of this study was to evaluate weight changes in patients with primary hypothyroidism after 6 weeks of initiation of treatment with levothyroxine. This prospective observational follow up study included 99 newly diagnosed primary hypothyroid patients of 18-60 years of age of both sexes. The weight and height of each patient were measured and body mass index (BMI) was calculated both at the time of enrollment and at the end of 6 weeks of treatment with levothyroxine, and variables at the baseline and at follow up were compared. 93 patients out of 99 completed follow-up at 6±1 weeks. There were significant reduction in TSH level (85.1±51.6 vs. 1.87±0.9 μIU/mL, mean±SD) and increase in FT4 level (0.49±0.19 vs. 1.4±0.78 ng/dL, mean±SD) at follow up in comparison to their baseline values. Among the participants, 90.3% lost body weight while 5.4% gained weight and 4.3% of subjects didn’t show any change in their weight at the end of the study. The mean body weight and mean BMI after levothyroxine replacement were significantly lower (weight 62.2±13.7 vs. 59.0±12.1 kg, BMI 25.1±4.6 vs. 23.8±4.1 Kg/M2, mean±SD) than the pretreatment values. The mean changes in body weight and BMI were 3.19±0.32 Kg (mean±SEM) and 1.31±0.14 Kg/M2 (mean±SEM) respectively. The mean changes in body weight and BMI did not differ significantly among subjects with different TSH categories. No statistically significant effect of any individual predictors like age, gender, and socioeconomic status, weight at baseline, baseline TSH, baseline FT4 and presence of thyroid autoimmunity was observed on weight change. Levothyroxine replacement was associated with a significant reduction of mean body weight and BMI at short-term follow up in our study, though not all patients experienced weight loss