Predictors of hypothyroidism after hemithyroidectomy: Development and validation of a clinical nomogram.

Abstract

Hypothyroidism after hemithyroidectomy remains common and may offset the perceived benefits of a less extensive operation. Reliable risk stratification tools for postoperative hypothyroidism after hemithyroidectomy are lacking. This study aimed to identify predictors of postoperative hypothyroidism and develop a clinically applicable risk model. A retrospective analysis of a prospectively maintained database was performed, including 791 patients who underwent hemithyroidectomy at a tertiary center (2017-2023). Patients with prior thyroid surgery, preoperative thyroid hormone therapy, radioactive iodine treatment, or complete thyroidectomy during follow-up were excluded. The primary outcome was initiation of levothyroxine. Independent predictors were identified using multivariable logistic and Cox regression analyses. A nomogram was developed and internally validated using bootstrap resampling. Among 507 included patients, 236 (46.6%) developed hypothyroidism within 12 months; 55.9% of cases occurred within 3 months. Independent predictors included family history of thyroid disease (odds ratio, 6.63; P = .006), elevated preoperative free triiodothyronine (odds ratio, 2.45; P = .006), thyroid-stimulating hormone >2.42 μIU/mL (odds ratio, 4.23; P < .001), specimen size ≥36.2 mm (odds ratio, 10.69; P = .001), thyroiditis in the surgical specimen (odds ratio, 48.21; P = .001), and carcinoma (odds ratio, 6.02; P = .012). A nomogram incorporating these variables enabled individualized risk estimation. The model demonstrated good discrimination (area under the curve, 0.745; 95% confidence interval, 0.703-0.788) and calibration. Hypothyroidism affects nearly half of patients after hemithyroidectomy, frequently within the first 3 months. This validated nomogram provides a practical tool for preoperative counseling and may inform tailored postoperative surveillance strategies.