Q J Med 2001; 94: 471-473
© 2001 Association of Physicians
Abnormal serum free thyroid hormone levels due to heparin administration
From the Departments of Medicine, and 1 Clinical Biochemistry, University Hospital of Wales, Cardiff, UK
Received 9 March 2001 Fractionated or unfractionated heparin may produce artefactual elevation in measured concentrations of free thyroid hormones. Although the specific cause is unknown, it may be a consequence of displacement of thyroid hormones from their binding sites by free fatty acids liberated in vitro. We describe four cases of heparin-induced abnormalities in free thyroid hormone measurements where some diagnostic confusion was generated. Increasing physician awareness of this poorly appreciated entity may avert diagnostic confusion and unnecessary investigation.
Address correspondence to Dr K. Laji, Diabetes Unit, Royal Glamorgan Hospital, Llantrisant, South Wales CF72 8XR. e-mail: laji{at}doctors.org.uk