There is an approximate 30% risk for hypothyroidism after hemithyroidectomy, according to the results of a systematic review and meta-analysis published in Endocrine.
To better understand the risk factors for and prevalence of subsequent hypothyroidism in patients who undergo hemithyroidectomy, researchers conducted a literature search in PubMed, Embase, and the Cochrane Library and examined data from 51 studies. The included studies were published between 1986 and 2019 and had cohorts of 14 to 1240 participants.
The weighted pooled risk for hypothyroidism after hemithyroidectomy was 29.9% (95% CI, 24.6-35.2), with a range of 0.6% to 68.1% between studies in the meta-analysis. In studies that reported rates of levothyroxine supplementation after the procedure, a similar prevalence rate of 29.2% (95% CI, 23.4-35.0) was noted for patients with confirmed hypothyroidism. When considering only patients who were euthyroid before hemithyroidectomy, the weighted pooled risk for postprocedure hypothyroidism was 31.8% (95% CI, 26.5-37.2).
A total of 34 studies reported risk factors associated with hypothyroidism after hemithyroidectomy. The review authors found that female sex (risk ratio [RR], 1.169; 95% CI, 1.040-1.314; P =.009), presence of lymphocyte infiltration (RR, 1.558; 95% CI, 1.203-2.018; P =.001), concomitant Hashimoto thyroiditis (RR, 1.48; 95% CI, 1.192-1.838; P =.000), and right side lobectomy (RR, 1.404; 95% CI, 1.075-1.835; P =.013) were predictors of postoperative hypothyroidism. Weight of the remaining thyroid gland was also significantly associated with hypothyroidism after the procedure, with a lighter weight associated with a greater likelihood of hypothyroidism (P =.000).
With regard to preoperative hormone levels, higher thyrotropin (>2.0 μIU/mL; RR, 2.955; 95% CI, 2.399-3.640; P =.000) and lower free thyroxine concentrations (standardized mean difference, -0.818; 95% CI, -1.623 to -0.013; P =.047) were predictive of posthemithyroidectomy hypothyroidism.
The researchers noted that the variation in thyrotropin reference ranges between the included studies likely introduced variability in hypothyroidism diagnoses and altered the overall prevalence rates.
“The risk of hypothyroidism following lobectomy should not be neglected and requires an assessment of factors that may predict its occurrence,” such as those highlighted in the results of this meta-analysis, the researchers concluded. “[W]e suggest that patients at high risk should carefully consider these factors when deciding which surgical procedure to receive.”
Li Z, Qiu Y, Fei Y, Xing Z, Zhu J, Su A. Prevalence of and risk factors for hypothyroidism after hemithyroidectomy: a systematic review and meta-analysis [published online July 7, 2020]. Endocrine. doi:10.1007/s12020-020-02410-5