Levothyroxine-Associated Thyrotoxicosis and Hyperbilirubinemia on Preoperative Screening Evaluation

Levothyroxine is a commonly prescribed medication for treatment of hypothyroidism in the United States. This drug is titrated based on weight and serial laboratory evaluation and is often very well tolerated with few adverse effects. Levothyroxine-associated liver injury and cholestatic disease are regarded as rare phenomena. We report an additional case of levothyroxine-associated hepatic dysfunction with resolution upon decreased dosage and continued tolerance of the medication.

We report a case of a 60-year-old male presenting for preoperative clearance for umbilical hernia repair with previous history of thyroidectomy for multinodular goiter. Laboratory work-up suggested thyrotoxicosis-associated hepatic dysfunction secondary to levothyroxine overtreatment with associated mixed hepatocellular and cholestatic pattern of injury. Extensive work-up failed to reveal other etiology of liver dysfunction and levothyroxine overtreatment was regarded as the likely cause. Complete resolution of the elevated hepatic enzymes occurred with decreased levothyroxine dosing and return of euthyroid state.

Although regarded as a rare phenomenon, levothyroxine use and drug-induced thyrotoxicosis should be considered as a possible etiology when evaluating hepatic dysfunction. This case highlights that levothyroxine may be safely continued following a dosing adjustment with noted resolution of hepatic enzyme abnormalities in certain clinical scenarios.