Pseudomalabsorption of levothyroxine
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K B Ain1, S Refetoff, H G Fein
1Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Md.
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.