Hypothyroidism leading to a syncopal episode: A reminder to check drug interactions/A case of iatrogenic hypothyroidism presented with cardioinhibitory syncope and resolved by thyroxine supplementation Reply

Abstract

We read with great interest the article: “A case of iatrogenic hypothyroidism presented with cardio-inhibitory syncope and resolved with levothyroxine supplementation” (1). Similarly we report a case of cardio-inhibitory syncope as a result of a drug interaction from an over the counter medication. A 65-year-old female with a past medical history significant for hypothyroidism, hypertension and obesity was brought into the emergency room after experiencing a syncopal episode. Electrocardiogram revealed sinus bradycardia with heart rate-40 beats/min and findings of a new first-degree atrioventricular block (PR interval 0.24 s). Head computed tomography (CT) did not reveal any evidence of an acute hemorrhagic stroke. Carotid Doppler examinations were negative for evidence of stenosis. A complete metabolic profile and complete blood count were unrevealing as well. Thyroid function studies revealed a thyroid stimulating hormone (TSH) level of 125 mIU/mL with free thyroxine (T4) of 0.19 ng/DL. Three months prior to this episode, the patients TSH was 2.2 mIU/mL. Patient had been taking levothyroxine 100 mcg every day for the past 5 years without any prior abnormalities in her thyroid function tests. Upon further questioning it was elicited that the patient had been also taking orlistat, an over the counter medication, to help lose weight under the guidance of a primary care physician. Orlistat was held immediately. Endocrinology was consulted and the patient was restarted on her home dose of levothyroxine as she had been therapeutic on prior to the initiation of levothyroxine. At a 6 month f/up, patient’s bradycardia and first degree AV block had resolved. Her repeat thyroid functions revealed TSH of 5 miu/mL and free T4 of 0.56 ng/dL. Orlistat is a gastrointestinal lipase inhibitor that reduces absorption of dietary fat by thirty percent (2). A few cases have been described in the literature to suggest that orlistat may prevent the absorption of levothyroxine. It has been proposed that orlistat may decrease the absorption of levothyroxine in the small intestine (3).