ACTA ENDOCRINOLOGICA (BUC)

Context. Understanding factors delaying recovery in thyrotoxicosis patients is crucial for optimizing treatment plan. Objective. This study aimed to identify predictive factors for the delayed thyroid function recovery in thyrotoxicosis patients. Design. The study is a retrospective review of medical records of adult thyrotoxicosis patients diagnosed at Kaohsiung Veterans General Hospital, Taiwan, from January 2014 to December 2021. The duration of follow-up for the main outcome was at least 18 months. Subjects and Methods. Patients newly diagnosed with thyrotoxicosis who were age > 18 years old, had a TSH level <0.1 μIU/mL, received CBZ or PTU treatment, and demonstrated a subsequent TSH increase to above 0.4 μIU/ mL, were included. Results. The study included 443 patients. The average time to achieve normalized TSH levels was 6.9 months. Key factors associated with delayed TSH normalization included higher body mass index (BMI) [odds ratio (OR) = 1.06, confidence interval (CI): 1.01–1.12], elevated serum free T4 levels (OR = 1.97; CI, 1.44–2.69), and treatment with propylthiouracil (OR = 2.66; CI, 1.33–5.32). In contrast, factors such as sex, age, season of diagnosis, and comorbidities did not significantly impact the rate of TSH normalization. Conclusion. The study highlights the importance of considering individual patient characteristics, such as BMI and initial free T4 levels, in thyrotoxicosis management. The findings suggest a potential preference for carbimazole over PTU in achieving faster TSH normalization. This research contributes to the understanding of thyrotoxicosis recovery and supports the need for personalized treatment approaches in clinical practice.