MON-473 Evaluating Conflicting Thyroid Function Tests in New Admissions: Discordance of TSH, FreeT4 and Clinical Status: A Clinical Challenge!

Background: It is not uncommon to encounter patients whose thyroid function tests (TFTs) seem mutually inconsistent or inconsistent with a patient’s clinical status, At times, the simplest reconciliation of the findings invokes a rare disorder that we are hesitant to accept. In this case, a clinically euthyroid patient presents with elevated TSH and Free T4 (FT4) suggestive of a TSH-producing tumor or of Thyroid Hormone Resistance. Clinical Case: A 72 yr-old man with cardiomyopathy on amiodarone is admitted to the Medical Service for treatment of anasarca. He had no symptoms or signs of thyroid dysfunction and was not taking L-T4, amphetamines or propranolol. Findings on exam included normal VS, runs of atrial tachycardia, and edema from feet to scrotum. Thyroid exam was normal. Serum creatinine was 2.24 mg/dl (NL: 0.67-1.17). Bili was 2.7 mg/dl (NL: 0.67-1.17); AST and ALT were normal, Chest x-ray revealed cardiomegaly with clear lung fields. Thyroid ultrasound revealed a normal size gland containing a few sub-centimetric nodules. On Day 2 The serum FT4, by analog assay, was elevated at 1.66 ng/dl (NL: 0.76-1.46) and TSH was elevated at 9.06 mIU/L (NL: 0.35-3.74), Anti-peroxidase and anti-thyroglobulin antibodies were negative. The Medical Service’ diagnosis was “amiodarone-induced thyroiditis.” The amiodarone was discontinued and diuresis was induced with bumetanide, Endocrinology consultation was requested On Day 4 the FT4 and TSH were still elevated at 1.62 and 10.1, respectively. FT4 by dialysis was not elevated at 1.62 ng/dl (NL: 0.9-2.2). The FT3 was 2.34 pg/ml (NL: 2.18-3.98). On Day 5 Anti-thyroxine antibodies and Thyroid Stimulating Immunoglobulins (TSI) were negative. Paired TSH samples with and without neutralization of Human Anti-Mouse Antibodies (HAMA) were identical: both elevated at 8.30 mIU/L (NL: 0.4-4.50). Serum Iodine was markedly elevated at 2288 mcg/L (NL: 52-109). The FT4 levels by analog assay therefore appear to have been falsely elevated (as indicated by the dialysis assay) though not by recognized factors such as thyroxine antibodies, amphetamines or propranolol. Continued observation is necessary to further assess the transience of the post-admission TFTs. Conclusion: In patients admitted to Acute Medical or Psychiatric Services, most combinations of high or low TSH and FT4 have been reported as well other aberrations of “non-thyroidal illnesses.” In patients with conflicting TFTs at admission, especially those who are clinically euthyroid, it is generally better to allocate a few weeks for observation and monitoring than to immediately launch into searches for rare disorders. This is especially important when multiple potentially thyro-active clinical states exist, such as renal and hepatic compromise, amiodarone use, and highly elevated iodine levels.