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.


METHODS
--Retrospective case series.


METHODS
--Referred care in two large tertiary care centers.


METHODS
--Four patients, seen within two decades, with clinical and biochemical hypothyroidism while receiving levothyroxine, were evaluated for selective malabsorption of this hormone.


METHODS
--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.
Ain
K B
KB
Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Md.
Refetoff
S
S
Fein
H G
HG
Weintraub
B D
BD
D000328:Adult; D005162:Factitious Disorders / Q000175:diagnosis; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000378:metabolism*; D007408:Intestinal Absorption; D008875:Middle Aged; D010349:Patient Compliance; D012189:Retrospective Studies; D013974:Thyroxine / Q000097:blood / Q000493:pharmacokinetics*; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D013974:Thyroxine