Hypothyroidism in Thyroid Carcinoma Follow-up: Orlistat May Inhibit the Absorption of Thyroxine

In 2005, a case was reported where a 46-year-old woman with papillary carcinoma of the thyroid developed symptomatic hypothyroidism after starting orlistat, a drug used to manage obesity by reducing fat absorption. Despite being compliant with her thyroxine medication post-thyroidectomy and radio-iodine ablation, her thyroid function tests showed a profound drop in thyroxine (T4) levels and a significant increase in thyroid-stimulating hormone (TSH) after beginning orlistat. Upon discontinuing orlistat and increasing her thyroxine dosage, her symptoms improved, and her TSH and T4 levels normalized. This case suggested that orlistat may interfere with the absorption of thyroxine, and it was the first reported instance of hypothyroidism in a patient taking both a TSH suppressive dose of thyroxine and orlistat. The authors emphasized the importance of healthcare providers being aware of this potential drug interaction in the management of thyroid cancer patients.