A Clinical Risk Score for Thyroid Hormone Therapy After Partial Thyroidectomy

The need for thyroid hormone therapy (levothyroxine [LT4]) after partial thyroidectomy varies with clinical factors, including the preoperative thyroid stimulating hormone (TSH) level and diagnosis. The goal of this study was to develop an easy-to-use clinical risk score to predict the need for LT4 after partial thyroidectomy.

This is a retrospective cohort study of patients who underwent partial thyroidectomy between 2013 and 2020 at a single institution. The primary outcome was postoperative LT4 therapy. Univariable and multivariable logistic regression evaluated the relationship between covariates and LT4 therapy. Covariates selected by lasso regression as significantly associated with LT4 therapy were incorporated into a weighted risk score. Performance characteristics for the risk score were assessed.

Of 425 patients, the median preoperative TSH was 1.4 uIU/mL interquartile range: 0.9-2.0), and 101 patients (23.8%) had a diagnosis of hypothyroidism. In total, 41.9% (n = 178) of patients required LT4 supplement after partial thyroidectomy. On multivariable logistic regression, non-Black race (odds ratio [OR]: 3.40, P < 0.001), preoperative TSH ≥1.59 (OR: 3.51, P < 0.001), and cancer diagnosis (OR: 2.08, P < 0.001) remained significantly associated with LT4 therapy and were incorporated into a clinical risk score. Rates of LT4 use increased with risk score points (0-2: 14%; 3-4: 34%; 5-6: 58%, 7-8: 75%). The model had a negative predictive value of 75% for LT4 therapy.

This simple risk score can be easily derived from data in the health record and can be used to counsel patients about likelihood of needing LT4 after partial thyroidectomy and guide clinical discussions about the extent of surgery in patients with thyroid nodules.