PSEUDOMALABSORPTION OF LEVOTHYROXINE

Objective. - The issue of patient compliance with pharmacological therapy vs malabsorption of medication was explored in the context of persistent hypothyroidism despite the administration of large doses of levothyroxine sodium. Design. - Retrospective case series. Setting. - Referred care in two large tertiary care centers. Patients. - Four patients, seen within two decades, with clinical and biochemical hypothyroidism while receiving levothyroxine, were evaluated for selective malabsorption of this hormone. Interventions. - Studies included serial measurements of thyroid hormone levels after a loading dose of levothyroxine or liothyronine sodium or evaluation with a double-labeled thyroxine tracer technique. Results were compared with studies of levothyroxine malabsorption in the medical literature. Results. - All patients were ultimately found to have normal (82% to 100%) absorption of oral levothyroxine. There was no evidence that malabsorption of levothyroxine can occur as an isolated abnormality. Conclusions. - Some patients exhibit a factitious disorder suggesting malabsorption of levothyroxine. When treating hypothyroidism, psychiatric issues may result in noncompliance with levothyroxine therapy.