Risk of Hypothyroidism following Hemithyroidectomy: Systematic Review and Meta-Analysis of Prognostic Studies

Abstract

The reported risk of hypothyroidism after hemithyroidectomy shows considerable heterogeneity in literature. The aim of this systematic review and meta-analysis was to determine the overall risk of hypothyroidism, both clinical and subclinical, after hemithyroidectomy. Furthermore, we aimed to identify risk factors for postoperative hypothyroidism. A systematic literature search was performed using several databases, including PubMed. Original articles in which an incidence or prevalence of hypothyroidism after primary hemithyroidectomy could be extracted were included. Study identification and data extraction were performed independently by two reviewers. In case of disagreement, a third reviewer was consulted. A total of 32 studies were included in this meta-analysis. Meta-analysis was performed using logistic regression with random effect at study level. The overall risk of hypothyroidism after hemithyroidectomy was 22% (95% confidence interval, 19-27). A clear distinction between clinical (supranormal TSH levels and subnormal thyroid hormone levels) and subclinical (supranormal TSH levels and thyroid hormone levels within the normal range) hypothyroidism was provided in four studies. These studies reported on an estimated risk of 12% for subclinical hypothyroidism and 4% for clinical hypothyroidism. Positive anti-thyroid peroxidase status is a relevant preoperative indicator of hypothyroidism after surgery. Effect estimates did not differ substantially between studies with lower risk of bias and studies with higher risk of bias. This meta-analysis showed that approximately one in five patients will develop hypothyroidism after hemithyroidectomy, with clinical hypothyroidism in one of 25 operated patients.