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.