Analysis of Clinical Factors for the Determination of Optimal Serum Level of Thyrotropin After Recombinant Human Thyroid-Stimulating Hormone Administration

Purpose To determine the optimal levels of thyroid-stimulating hormone (TSH) levels after administration of recombinant human TSH (rhTSH) to patients with differentiated thyroid cancer (DTC), we have analyzed the clinical parameters that affected the degree of the increase in serum levels of TSH. Methods We retrospectively analyzed 276 patients with differentiated thyroid cancer (DTC), post-thyroidectomy and remnant ablation. Pearson's correlation coefficient test was used to evaluate the correlation between serum levels of TSH after rhTSH stimulation and various clinical factors, including age, sex, height, weight, body mass index (BMI), body surface area (BSA), serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate (GFR). Linear regression analysis was used to determine the predictors of the degree of increase in serum TSH level after rhTSH stimulation. Results After the rhTSH injections, all subjects achieved TSH levels of >30 mu U/mL, with a mean of 203.8 +/- 83.4 mu U/mL. On univariate analysis, age (r=0.255) and serum creatinine (r=0.169) level were positive predictors for higher levels of serum TSH after rhTSH stimulation, while weight (r=-0.239), BMI (r=-0.223), BSA (r=-0.217), and estimated GFR (r=0.199) were negative predictors. Multiple linear regression analysis revealed that serum creatinine was the most powerful independent predictor for serum levels of TSH, followed by age, BSA, and BMI. Conclusions An increment in serum TSH after rhTSH stimulation was significantly affected by age, BSA, BMI, and creatinine, with creatinine being the most powerful predictor. By understanding the difference in the increased levels of TSH in various subjects, their dose of rhTSH can be adjusted during scheduling for radioiodine ablation, or during follow-up (recurrence surveillance) after surgery and ablation.