Biochemical TSH Response and Short-Term Tolerability of Recombinant Human TSH versus Levothyroxine Withdrawal in Patients with Differentiated Thyroid Carcinoma

Abstract

Recombinant human thyroid-stimulating hormone (rhTSH) and levothyroxine withdrawal are commonly used to increase serum thyroid-stimulating hormone (TSH) before radioactive iodine procedures in patients with differentiated thyroid carcinoma. These approaches differ in their duration, biochemical response and associated symptoms. Objective: To compare the serum TSH response and short-term tolerability of rhTSH administration and levothyroxine withdrawal in patients with differentiated thyroid carcinoma. Methods: This prospective nonrandomized comparative study included 50 patients with differentiated thyroid carcinoma treated at the Bannu Institute of Nuclear Medicine, Oncology and Radiotherapy, Pakistan, from February to July 2019. Twenty-seven patients received two intramuscular injections of 0.9 mg rhTSH administered 24 hours apart while continuing levothyroxine, whereas 23 patients underwent levothyroxine withdrawal for four to eight weeks. Serum TSH was measured at baseline and after stimulation. A serum TSH concentration of at least 30 mIU/L was considered an adequate biochemical response. Final TSH concentrations were compared using the Mann–Whitney U test, and the proportions of patients reporting symptoms were compared using Fisher’s exact test. Results: In the rhTSH group, mean serum TSH increased from 0.16 ± 0.19 mIU/L at baseline to 45.46 ± 9.65 mIU/L after the first dose and 84.88 ± 9.42 mIU/L after the second dose. Following levothyroxine withdrawal, mean serum TSH increased from 0.91 ± 1.71 to 51.20 ± 8.88 mIU/L. All patients in both groups achieved serum TSH concentrations of at least 30 mIU/L. Final stimulated TSH concentrations were significantly higher in the rhTSH group than in the withdrawal group (median, 86.30 versus 47.90 mIU/L; Mann–Whitney U test, p < 0.001). At least one treatment-related symptom was reported by 4 of 27 patients receiving rhTSH and 17 of 23 patients undergoing levothyroxine withdrawal (14.8% versus 73.9%; Fisher’s exact test, p < 0.001). Conclusion: Both preparation methods produced adequate biochemical TSH stimulation in all patients. Recombinant human TSH achieved stimulation more rapidly and was associated with fewer reported short-term symptoms than levothyroxine withdrawal. However, because allocation was nonrandomized and radioiodine treatment outcomes were not evaluated, the findings should not be interpreted as evidence of superior oncological effectiveness.