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Micah D Will, Geza S Bodor, A Patient with Widely Fluctuating Thyroid-Stimulating Hormone Measurements, Clinical Chemistry, Volume 60, Issue 10, 1 October 2014, Pages 1349–1350, https://doi.org/10.1373/clinchem.2013.218164
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Case Description
A 56-year-old man had a thyroid-stimulating hormone (TSH)4 value of 22.5 μIU/mL (reference interval 0.4–4.6 μIU/mL). The increased TSH prompted review of his previous thyroid testing results (Table 1). The patient's history revealed a diagnosis of papillary thyroid carcinoma 8 months prior, which was treated with total thyroidectomy and 131I radioablation followed by l-thyroxine (Synthroid) treatment. This was his first follow-up visit for evaluation of recurrence of his disease.
Previous thyroid testing results.
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Answers
Radioiodine (131I) is used for radioablation of thyroid remnants (1), as was done on March 12, 2012 for our patient, and to scan for recurrence of thyroid cancer (2), as was done on November 2, 2012. Increased TSH, achieved by withholding thyroid supplements or injecting recombinant human TSH (rhTSH), enhances 131I uptake (3, 4) that, in turn, will increase the sensitivity of whole body scan for residual or recurrent thyroid cancer. Two doses of 0.9 mg rhTSH, 24 hours apart, are optimal to achieve peak TSH concentrations of 60–240 μIU/mL 24 h after the second dose, and to maintain a 25–30 μIU/mL therapeutic concentration on the day of 131I administration (4, 5). The increased TSH concentration was due in our patient to 2 injections of rhTSH on the days prior to the laboratory testing. Although the measured TSH concentration (22.5 μIU/mL) was slightly lower than desired, whole body radioiodine scan was performed, and it did not disclose signs of recurrence.
