[Hypothyroidism due to pseudo-malabsorption of levothyroxine--Case 12/2009]

Hypothyroidism is a common endocrine disorder which is easily treatable by an appropriate thyroid hormone replacement therapy in the majority of patients. In some patients, hypothyroidism is refractory to oral levothyroxine substitution. Common causes of lack of response to levothyroxine replacement comprise non-compliance and impaired absorption.

We report on a 32-year-old women who presented with persistent clinical and biochemical signs of hypothyroidism after thyroid surgery for Graves' disease despite high doses of levothyroxine replacement therapy.

An extensive evaluation for malabsorption syndromes proofed negative. Supervised absorption tests of two different levothyroxine preparations were normal. Pseudomalabsorption was presumed, though the patient continued to deny noncompliance. Supervised once weekly oral levothyroxine was advised.

Non-compliance with medical therapy should be considered in patients with treatment-refractory hypothyroidism prior to initiation of an extensive evaluation for malabsorption syndromes. Supervised levothyroxine absorption test is a useful tool in the diagnostic workup for supposed pseudomalabsorption. In non-compliant patients, supervised once weekly levothyroxine replacement appears to be a safe and well-tolerated treatment option.