High Serum TSH Level Is Associated With Progression of Papillary Thyroid Microcarcinoma During Active Surveillance

Thyroid-stimulating hormone (TSH) is a growth factor affecting initiation or progression of papillary thyroid cancer (PTC), which supports TSH suppressive therapy in patients with PTC. In patients with papillary thyroid microcarcinoma (PTMC) during active surveillance, however, the association between serum TSH level and growth of PTMC has not been demonstrated.

We analyzed 127 PTMCs in 126 patients under active surveillance with serial serum TSH measurement and ultrasonography.

The patients were categorized into groups with the highest, middle, and lowest time-weighted average of TSH (TW-TSH). PTMC progression was defined as a volume increase of ≥50% compared with baseline. Kaplan-Meier survival analysis according to TW-TSH groups and Cox proportional hazard modeling was performed. We identified the cutoff point for TSH level by using maximally selected log-rank statistics.

During a median follow-up of 26 months, PTMC progression was detected in 28 (19.8%) patients. Compared with the lowest TW-TSH group, the adjusted hazard ratio (HR) for PTMC progression in the highest TW-TSH group was significantly higher [HR 3.55; 95% confidence interval (CI), 1.22 to 10.28; P = 0.020], but that in the middle TW-TSH group was not (HR 1.52; 95% CI, 0.46 to 5.08; P = 0.489). The cutoff point for the serum TSH level for PTMC progression was 2.50 mU/L.

Sustained elevation of serum TSH levels during active surveillance is associated with PTMC progression. Maintaining a low-normal TSH range with levothyroxine treatment during active surveillance of PTMC might be considered in future studies.