Eficácia de dose única de rhTSH em atingir TSH > 30 mUI/L em pacientes portadores de carcinoma diferenciado de tireoide submetidos a tratamento com Iodo-131

Abstract

Differentiated thyroid carcinoma (DTC), especially the papillary and follicular subtypes, is the most common thyroid malignancy, and its incidence has been increasing globally. Radioisotopic therapy with iodine-131 (RIT) is widely recommended after total thyroidectomy, particularly for patients at intermediate/high risk. The use of recombinant human TSH (rhTSH) to stimulate iodine-131 uptake during RIT was approved by the European Medicines Agency in 2005 and by the United States Food and Drug Administration in 2007. In the standard protocol, 0.9 mg of rhTSH is administered intramuscularly on two consecutive days, followed by a therapeutic dose of iodine-131 on the third day. Unlike the traditional method of levothyroxine (LT4) withdrawal, this protocol allows the continuation of LT4, thereby avoiding the symptoms and metabolic consequences of profound hypothyroidism. However, its high cost remains an important limitation in our setting. Therefore, this study evaluated whether a single intramuscular dose (0.9 mg) of rhTSH, instead of the currently recommended two doses, is sufficient to achieve the target TSH level (>30 mIU/L) currently recommended for performing RIT. This cross-sectional study included 88 patients. The Day 1 TSH level (TSH D1), defined as the primary outcome, was evaluated in relation to sex, age, body weight, recurrence risk (ATA 2025), baseline TSH values, and the interval between TSH measurements. A single dose of rhTSH substantially increased TSH levels to >30 mIU/L in all patients. Age and body weight were independently associated with TSH D1. Historical and preclinical data support the biological plausibility of this response. These preliminary results support the potential of single-dose rhTSH as a cost-effective and clinically feasible alternative in selected patients with DTC. Future comparative clinical trials should assess iodine uptake, therapeutic response, and long-term oncologic outcomes.