https://orcid.org/0000-0003-2873-587X
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William Butler, Melissa Sawyer Falcon, Daniel S Herman, Ping Wang, Normal Thyroid-Stimulating Hormone and Elevated Free Thyroxine in a Patient Presenting with Self-Reported Heart Palpitations, Clinical Chemistry, Volume 71, Issue 4, April 2025, Pages 445–448, https://doi.org/10.1093/clinchem/hvae177
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Case Description
A 21-year-old male with a history of acute lymphoblastic leukemia in remission presented to endocrinology for consultation regarding abnormal thyroid function tests and self-reported heart palpitations that began 7 months prior. Although the patient reported mild weight loss, he denied other symptoms typically associated with hyperthyroidism including diarrhea, anxiety, and tremor. His family history was notable for Graves disease in his father and unspecified thyroid dysfunction in his maternal aunt.
Physical examination demonstrated a normal-sized thyroid gland, without palpable nodules. At the time of examination, the patient had a normal heart rhythm with no abnormal sounds noted on auscultation. Review of the patient’s most recent thyroid function studies demonstrated a thyroid-stimulating hormone (TSH) concentration of 1.360 uIU/mL [0.450–4.500 uIU/mL] and free thyroxine (FT4) concentration of 2.41 ng/dL (31.0 pmol/L) [0.82–1.77 ng/dL (10.5–22.8 pmol/L)] (Table 1). Results from a comprehensive metabolic panel (common electrolytes and tests of liver and kidney function) did not show any significant biochemical abnormalities. Additional laboratory studies showed a normal concentration of total triiodothyronine (TT3) and no presence of thyroid-stimulating immunoglobulins. To rule out the possibility that the elevation in FT4 was due to a laboratory interference, equilibrium dialysis-mass spectrometry was performed which confirmed the presence of an elevated FT4 (3.7 ng/dL (47.6 pmol/L) [0.8–1.7 ng/dL (10.3–21.9 pmol/L)]). Additional studies showed a slightly elevated free triiodothyronine (FT3) of 4.9 pg/mL (7.6 pmol/L) [2.0–4.4 pg/mL (3.1–6.8 pmol/L)], which persisted on subsequent evaluations.
