PREDICTORS OF TIME TO BIOCHEMICAL EUTHYROIDISM IN TOXIC GOITER PATIENTS TREATED WITH ANTI-THYROID DRUGS: A FIVE-YEAR RETROSPECTIVE COHORT STUDY

ABSTRACT

Introduction: Toxic goiter is a common endocrine disorder requiring long-term anti-thyroid drug therapy, yet evidence on time to biochemical euthyroidism and its predictors is limited in resource-limited settings. This study aimed to determine time to biochemical euthyroidism and its predictors among patients with toxic goiter treated with anti-thyroid drugs at Wallaga University Comprehensive Specialized Hospital.

Methods: A five-year retrospective cohort study was conducted using 120 patient records selected from 143 eligible cases between January 1, 2021 and December 31, 2025. Data were collected using a structured checklist via Epi-data version 3.1 and analyzed using SPSS version 27. The Kaplan–Meier survival curve with log-rank test was used to compare differences in time to biochemical euthyroidism across categorical variables. Variables with a p-value <0.25 in bivariable analysis were entered into the multivariable Cox proportional hazards regression model. The proportional hazards assumption was assessed using Schoenfeld residuals and log-minus-log survival plots, and no significant violation was observed. Model fitness was evaluated using the Cox–Snell residual goodness-of-fit test, which indicated that the final model adequately fitted the data. Statistical significance was declared at p < 0.05.

Results: The response rate was 83.9%. The mean age of participants was 38.6 ± 12.4 years. The median time to biochemical euthyroidism was 6 months, based on Kaplan–Meier survival analysis. Rural residence (AHR = 0.68, 95% CI: 0.50, 0.92) and higher baseline FT4 levels (AHR = 0.94, 95% CI: 0.90, 0.98) were significantly associated with delayed time to euthyroidism.

Conclusion and recommendation: Although a substantial proportion achieved euthyroidism early, variability in response resulted in a broader distribution of time to normalization. Rural residence and higher baseline FT4 levels were significant predictors of delayed response. Strengthening early diagnosis, improving follow-up systems, and enhancing rural healthcare access are essential to improve treatment outcomes.

Keywords: Toxic goiter, biochemical euthyroidism, survival analysis, Ethiopia