INTRODUCTION: Thyroxine supplementation of patients with hypothyroidism is 
usually simple. A few patients, however, continue to present elevated TSH levels 
despite large doses of L-thyroxine.
CASE: We report the case of a 71-year-old women who had had a thyroidectomy 10 
years earlier and had since been hospitalized repeatedly for profound 
hypothyroidism. Despite her consistent claims of good adherence to her treatment 
regimen, we considered the diagnosis of L-thyroxine pseudomalabsorption and 
confirmed it by thyroid hormone absorption tests.
DISCUSSION: L-thyroxine pseudomalabsorption due to concealed poor treatment 
adherence should be considered after ruling out drug or dietary interference and 
true organic malabsorption. Diagnosis of this factitious disease can be 
confirmed by L-thyroxine absorption tests.