THYROID STIMULATING HORMONE EVALUATION BETWEEN THREE AND FOUR WEEKS OF LEVOTHYROXINE WITHDRAWAL IN PATIENTS WITH DIFFERENTIATED THYROID CARCINOMA

Most patients with differentiated thyroid cancer (DTC) would require radioactive iodine (RAI) ablation therapy with I-131. Before RAI ablation therapy, levothyroxine is withheld for four to six weeks to increase TSH to over 30 mIU/L. Most people develop hypothyroidism on levothyroxine withdrawal. Reducing levothyroxine withdrawal from four to three weeks would enhance health and hypothyroidism symptoms. This study aims to evaluate the thyroid-stimulating hormone level after three and four weeks of levothyroxine withdrawal in patients with DTC in the Northern Malaysia population. All DTC patients undergoing RAI ablation therapy from January 2018 to November 2019 were enrolled. TSH levels were evaluated three and four weeks after discontinuing levothyroxine. Clinical data were analysed using IBM SPSS (Statistical Package for the Social Sciences) version 26.0.0. One hundred four patients with a mean age of 47.06 years were recruited. Most patients (77.88%) had papillary thyroid carcinoma (PTC) and were female (80.77%) and Malay (53.85%). By week three of levothyroxine withdrawal, 88.46% of patients had TSH levels above 30 mIU/L, with an average of 66.89 mIU/L, and at week four, 99.04% of patients had TSH levels above 30 mIU/L. Cohen's kappa measurement of the agreement was 0.139 between weeks three and four. A TSH level greater than 30 mIU/L was detected in 88.46% of patients who had discontinued levothyroxine for three weeks and 99.04% after four weeks. It is recommended to review the TSH level at 3 weeks instead of 4 weeks in patients who could not tolerate hypothyroidism symptoms.