Monitoring Thyrotropin in Veterans With Thyroid Nodules

After the initial thyroid nodule diagnosis, a patient's thyrotropin is often monitored. However, the American Thyroid Association guidelines do not offer recommendations for follow-up thyrotropin testing for patients with thyroid nodules who have no history of conditions or known medications that affect thyroid hormone levels.

At the Veterans Affairs Dayton Healthcare System in Ohio, we conducted a retrospective chart review from January 2010 to December 2016 of 100 patients diagnosed with ≥ 1 thyroid nodule on imaging studies who had normal blood thyrotropin at the time of nodule diagnosis. The thyrotropin value was studied at and after diagnosis. A 95% CI was determined for the true population rate of patients with an abnormal thyrotropin at their most recent testing. χ² tests for categorical variables and independent sample t tests for continuous variables were used to compare the abnormal and normal most recent thyrotropin groups.

One hundred patients (male [83%], White race [82%]) with normal thyrotropin at nodule diagnosis had thyrotropin monitoring for a mean (SD) of 5.7 (2.5) years. Six of 100 patients (6%; 95% CI, 2.5%-12.7%) developed abnormal thyrotropin levels in a mean (SD) of 6.9 (3.1) years. When comparing the 6 patients with abnormal thyrotropin vs the 94 with normal thyrotropin, there were no significant differences in sex (P = .99), race (P = .55), age at diagnosis (P = .12), initial thyrotropin level (P = .24), most recent thyrotropin level (P = .98), or time from diagnosis to most recent thyrotropin level (P = .23).

This study found no significant change in thyrotropin levels over time in patients with thyroid nodules and no history of medical conditions or medications known to affect thyrotropin levels. Monitoring thyrotropin over time may not be required in these patients. More studies are needed to provide additional data on thyrotropin monitoring for thyroid nodules so that clinicians can make evidence-based decisions.