Pseudomalabsorption of thyroid hormones: case report and review of the literature

Abstract

Many causes of thyroxine malabsorption are described in the literature, but the most common cause of failure of thyroxine therapy is poor patient compliance, or pseudomalabsorption. We describe the case of a female patient who underwent total thyroidectomy for Basedow-Graves disease. Post-operatively, several treatment regimens were employed to achieve euthyroidism, but only injectable thyroxine was found to be effective. To exclude levothyroxine malabsorption, the patient was hospitalized in a hypothyroid state while a single oral test dose of levothyroxine (1000 μg) was administered. Within 4 hours a decrease of TSH level (from 59.7 to 55.6 μUI/ml) and a significant increase in free T4 levels (from 0.8 to 15.5 pg/ml) was observed, eliminating a malabsorption problem. The cause of resistance to thyroid hormone therapy was poor patient compliance, leading to the designation of this as a case of pseudomalabsorption.