Fellow Jersey Shore University Medical Center Neptune, New Jersey, United States
Introduction : Abnormal thyroid function values are commonly seen in the hospital and physicians must be vigilant in ruling out confounding factors. Many medications administered in hospital settings, including the very commonly used heparin, are known to cause abnormal levels. This case describes an interesting presentation of suspected amiodarone induced thyrotoxicosis which was deemed to be a heparin induced lab abnormality.
Case(s) Description : A 78-year-old female presented to the emergency room with acute onset bilateral lower extremity numbness weakness and urinary incontinence. Her medical history included non small cell lung cancer, atrial fibrillation maintained on amiodarone, and history of bilateral pulmonary embolisms maintained on apixaban. An MRI of the spine was obtained and showed intradural mass at the thoracic level with compression of the spinal cord. Her apixaban was stopped and heparin drip was initiated in anticipation of possible surgical intervention, she was also started on high dose steroids. Thyroid function tests were obtained on admission as part of the investigation of her weakness and revealed an elevated FT4 of 1.91 ng/dL and low TSH 0.410 uIU/mL. This was confirmed on a repeat sample and additional labs revealed negative thyroid antibodies and elevated thyroglobulins. A thyroid ultrasound was performed which showed a heterogeneous gland with multiple small nodules with normal vascularity. Based on these findings and her history of amiodarone use, drug induced thyroiditis was suspected. Since this patient had already been initiated on high dose steroids we expected FT4 to trend downwards, however it was observed that the FT4 continued to elevate higher. Due to increasing levels of FT4 she was initiated on methimazole and cholestyramine, however no improvement was seen in her thyroid function tests. On day 3 of her admission patient was scheduled for resection of her spinal cord lesion and heparin was held at midnight. The following morning it was observed that her FT4 had trended downward and she was discharged without any additional thyroid medications. Patient was seen at outpatient for follow up where she continued to be euthyroid without ongoing treatment.
Discussion : Amiodarone is a known cause of abnormal thyroid function however other medications must be considered and ruled out as possible causes of falsely abnormal values especially if there are discrepancies in their clinical course.
