Hyperthyroidism is common, diagnosed in 2.0% of women and 0.2% of men worldwide. The main treatments for hyperthyroidism are antithyroid drugs, radioiodine, and surgery. Thyroidectomy has been reported to be an effective, safe, and cost-saving method and to have the lowest recurrence rate compared with radioiodine and antithyroid drugs.1 However, total thyroidectomy requires more careful and accurate hemostasis when performed in patients with hyperthyroidism vs patients with normal thyroid function (euthyroidism).2 The aim of this nonrandomized clinical trial was to compare the incidence of morbidity after total thyroidectomy among patients with preoperative hyperthyroidism vs patients with preoperative euthyroidism. Methods We performed an analysis of data collected in the FOThyr (Medico-Economic Evaluation Comparing the Use of Ultrasonic Scissors to the Conventional Techniques of Haemostasis in Thyroid Surgery by Cervicotomy; NCT01551914) study.3 The FOThyr study, conducted from March 2012 to June 2014, was a prospective randomized multicenter clinical trial comparing the use of a disposable hemostatic device with the use of conventional hemostasis for total thyroidectomy among adult patients. The study protocol was reviewed and approved by a regional ethics committee (Comité de Protection des Personnes Ouest IV) and by the national data protection authority in France (Commission Nationale de l’Informatique et des Libertés). The study was performed in accordance with the Guideline for Good Clinical Practice and the Declaration of Helsinki. All patients provided written informed consent before inclusion. All patients planning to undergo total thyroidectomy were eligible for inclusion if they had Graves disease, euthyroid or hyperthyroid goiter, or any thyroid nodule requiring total thyroidectomy via cervicotomy. In accordance with guidelines from the French Society of Endocrinology (http://www.sfendocrino.org), all patients with overt hyperthyroidism (ie, high triiodothyronine and/or thyroxine hormone levels) received preoperative antithyroid drugs to normalize thyroid hormone levels. An evaluation of recurrent laryngeal nerve function was systematically conducted after each surgery. A vocal cord examination with nasofibroscopy was performed before hospital discharge and 6 months after surgery to monitor potential postoperative recurrent laryngeal nerve abnormality. Postoperative hypocalcemia was defined as a serum calcium level lower than 8.0 mg/dL (corrected for albumin level; to convert to mmol/L, multiply by 0.172) at postoperative day 2, and definitive hypocalcemia was defined as a serum calcium level lower than 36.0 mg/dL at 6 months after surgery. Clinical observation was performed during hospitalization to diagnose potential hematomas. Data analysis was performed using SAS software, versions 9.2 and 9.3 (SAS Institute). Data were analyzed from September to December 2017. Results From March 2012 to June 2014, 1250 patients with usable data (mean [SD] age, 50.9 [13.3] years; 997 women [79.8%]) were enrolled at 14 sites in France. At the preoperative consultation, 255 patients (20.4%) had hyperthyroidism, and 995 patients (79.6%) had euthyroidism. All preoperative patient characteristics are shown in Table 1. Postoperative abnormal vocal cord mobility was diagnosed in 130 of 1250 patients (10.4%), representing 102 of 995 patients (10.3%) in the euthyroidism group and 28 of 255 patients (11.0%) in the hyperthyroidism group (difference, 0.70%; 95% CI, −0.05% to 0.04%) (Table 2). Definitive recurrent nerve palsy (RNP) was diagnosed in 12 patients (1.0%), representing 10 patients (1.0%) in the euthyroidism group and 2 patients (0.8%) in the hyperthyroidism group (difference, 0.22%; 95% CI, −0.01% to 0.02%). Postoperative hypocalcemia was diagnosed in 250 patients (20.0%), representing 196 patients (19.7%) in the euthyroidism group and 54 patients (21.2%) in the hyperthyroidism group (difference, 1.50%; 95% CI, −0.08% to 0.04%). Definitive hypocalcemia was diagnosed in 25 patients (2.0%), representing 19 patients (1.9%) in the euthyroidism group and 6 patients (2.4%) in the hyperthyroidism group (difference, 0.48%; 95% CI, −0.03% to 0.02%). Discussion In the present study, preoperative hyperthyroidism was not associated with substantial increases in the incidence of complications (neither postoperative nor definitive hypocalcemia, RNP, or hematoma) after total thyroidectomy among patients who received preoperative antithyroid drugs. These morbidity results may be surprising, given that one would expect a substantial difference between patients with preoperative hyperthyroidism and those with euthyroidism. However, our results are consistent with those of other studies.4,5 This nonrandomized clinical trial was large (1250 patients), with minimal postoperative missing data. Data collection was thorough with regard to preoperative and immediate postoperative data but less thorough with regard to late postoperative data, especially for RNP incidence. Approximately 50% of postoperative patients with RNP chose not to undergo postoperative laryngoscopy at 6 months, which may have produced underestimation of definitive RNP. However, Lifante et al6 have reported an association between the incidence of definitive and immediate postoperative palsies. This study has 2 primary limitations. First, the FOThyr study, from which the sample for the present study was obtained, was not designed to assess morbidity but to evaluate the 6-month clinical efficacy and cost-effectiveness of using ultrasonic scissors (HARMONIC FOCUS; Johnson & Johnson) compared with conventional hemostasis for thyroidectomy.3 Second, data on thyroid-stimulating hormone levels were only collected at the first preoperative consultation; we did not collect data on thyroid-stimulating hormone, triiodothyronine hormone, or thyroxine hormone levels on the day of surgery. Because the study lacked data on thyroid hormone levels immediately before surgery, the effectiveness of preoperative treatments could not be assessed. Medical treatment should precede surgery. However, the results of this large nonrandomized clinical trial may encourage endocrine surgeons to reassure and motivate patients to undergo total thyroidectomy as a definitive treatment for hyperthyroidism.