Objectives: Orlistat is used in the treatment of obesity while hypothyroidism is treated with levothyroxine. In this study, the effect of orlistat treatment on thyroid stimulating hormone (TSH) was investigated. Methods: The files of the patients who were followed up with the diagnosis of obesity and hypothyroidism were evaluated retrospectively. Patients with a body mass index (BMI) > 40 and receiving levothyroxine replacement therapy were included in the study. Group 1 consisted of 37 patients who received orlistat and levothyroxine while group 2 consisted of patients who received levothyroxine without orlistat. BMI and TSH values of patients were compared at baseline and at third month. Results: Despite group 1 having mild increase in TSH at third month compared to baseline, no statistically significant difference was observed (p:0.328). No differences were observed between TSH values of group 2 at baseline and third month (p: 0.380). When BMI of group 1 were compared at baseline and third month, it was found to be statistically lower (p<0.01). In group 2, BMI were significantly lower when baseline values were compared with third month (p<0.01). Conclusion: It would be appropriate to closely monitor thyroid function tests in patients on levothyroxine following initiation of orlistat treatment. Keywords: Hypothyroidism, levothyroxine, obesity, orlistat.
Corresponding Author: Bunyamin Aydin