(CSEMP001) A CASE OF DISCORDANCE IN THYROID FUNCTION TEST

Thursday, October 26, 2023

15:15 – 15:30 EST

Location: ePoster Screen 1

Disclosure(s):

Wedyan M. Aboznadah: No financial relationships to disclose

Oriana Hoi Yun Yu, MD: No financial relationships to disclose

Sneha Sheth, MD: No financial relationships to disclose

Background: The purpose of this paper is to present an algorithmic approach to trouble shooting possible errors when interpreting thyroid function tests. In the analysis of this specific case, an 87-year-old female presented with a discordant thyroid function test with an elevated thyroid stimulating hormone (TSH), elevated thyroxine level (T4) and no clinical symptoms of hyperthyroidism.

METHODS AND RESULTS: An 87-year-old female was referred from her family doctor for repeated abnormal thyroid function tests. She was overall well with no symptoms, including no palpitations, weight changes or changes in bowel movements. She denied any history of heat intolerance. Physical examination was unremarkable with no signs of hyper- or hypothyroidism. On presentation the TSH was 7.54mU/L (reference range of 0.4 – 4.5) and free T4 was 36.9pmol/L (reference range of 9-26). A repeated result showed a TSH of 6.88mU/L and free T4 of 36pmol/L. A computer tomographic scan of the head did not show a pituitary adenoma suggestive of TSHoma. A thyroid ultrasound showed low color flow doppler indicating no abnormal vascularity. After an exhaustive work- up other considerations were explored in the interpretation of discordant TFTs including: syndrome of inappropriate TSH secretion, autoantibodies, possible heterophilic interference, thyroid hormone autoantibodies assay-specific interference and resistance to thyroid hormone beta. After sending the patient’s specimen to three different laboratories utilizing different assays, it was concluded that there may be a potential interference in the thyroid function tests.

Conclusion: This patient’s thyroid function tests were done at three different labs, which resulted in disconcordant results. This case report aims to present an algorithmic approach to abnormal thyroid function tests including when to suspect rare causes of elevated TSH which may be related to TSHoma, heterophilic antibody interference, and thyroid hormone autoantibodies assay-specific interference.