Abstract: We included five RCTs with a total of 886 participants; 172 were randomised to total thyroidectomy, 383 were randomised to bilateral subtotal thyroidectomy, 309 were randomised to the Dunhill procedure and 22 were randomised to either bilateral subtotal thyroidectomy or the Dunhill procedure. Follow-up ranged between six months and six years. One trial had three comparison arms. All five trials were conducted in university hospitals or tertiary referral centres for thyroid disease. All thyroidectomies were performed by experienced surgeons. The overall quality of the evidence ranged from low to moderate. In all trials, blinding procedures were insufficiently described. Outcome assessment for objective outcomes was blinded in one trial. Surgeons were not blinded in any of the trials. One trial blinded participants. Attrition bias was a substantial problem in one trial, with 35% losses to follow-up. In one trial the analysis was not carried out on an intention-to-treat basis. Total thyroidectomy was more effective than subtotal thyroidectomy techniques (both bilateral subtotal thyroidectomy and the Dunhill procedure) at preventing recurrent hyperthyroidism in 0/150 versus 11/200 participants (OR 0.14 (95% CI 0.04 to 0.46); P = 0.001; 2 trials; moderate quality evidence). Total thyroidectomy was also more effective than bilateral subtotal thyroidectomy at preventing recurrent hyperthyroidism in 0/150 versus 10/150 participants (odds ratio (OR) 0.13 (95% confidence interval (CI) 0.04 to 0.44); P = 0.001; 2 trials; moderate quality evidence). Compared to bilateral subtotal thyroidectomy, the Dunhill procedure was more likely to prevent recurrent hyperthyroidism in 20/283 versus 8/309 participants (OR 2.73 (95% CI 1.28 to 5.85); P = 0.01; 3 trials; low quality evidence). Total thyroidectomy compared with subtotal thyroidectomy conferred a greater risk of permanent hypocalcaemia/hypoparathyroidism in 8/172 versus 3/221 participants (OR 4.79 (95% CI 1.36 to 16.83); P = 0.01; 3 trials; low quality evidence). Effects of the various surgical techniques on permanent recurrent laryngeal nerve palsy and regression of Graves' ophthalmopathy were neutral. One death was reported in one study in year three of follow-up. No study investigated health-related quality of life or socioeconomic effects. Total thyroidectomy is more effective than subtotal thyroidectomy (both bilateral subtotal thyroidectomy and the Dunhill procedure) at preventing recurrent hyperthyroidism in Graves' disease. The type of surgery performed does not affect regression of Graves’ ophthalmopathy. There was some evidence that total thyroidectomy compared with subtotal thyroidectomy conferred a greater risk of permanent hypocalcaemia/hypoparathyroidism, which however, was not seen in comparison with bilateral subtotal thyroidectomy. Permanent recurrent laryngeal nerve palsy did not seem to be affected by type of thyroidectomy. Health-related quality of life as a patient-important outcome measure should form a core determinant of any future trial on the effects of thyroid surgery for Graves' disease.

Plain-language summary: We identified five randomised controlled studies that were relevant to the review question that directly compared different thyroidectomy surgical techniques. A total of 886 participants were included in the studies and follow-up was between six months and six years. All five studies were conducted in university hospitals or tertiary referral centres for thyroid disease. The countries involved were Germany, Sweden, Poland and Taiwan. No study was performed in an outpatient setting. Total thyroidectomy is likely to give better control of hyperthyroidism compared to subtotal thyroidectomy (8 or 9 people out of 1000 will experience recurrence of hyperthyroidism after total thyroidectomy compared with 55 to 67 people out of 1000 after subtotal thyroidectomy). There is some evidence to suggest permanently low blood calcium (hypoparathyroidism) is more likely in total thyroidectomy compared to subtotal thyroidectomy (59 people out of 1000 after total thyroidectomy compared with 14 people out of 1000 after subtotal thyroidectomy will experience this side effect). Eye symptoms as well as permanent damage to the recurrent laryngeal nerve appear to be unrelated to the choice of surgical technique. Deaths were rarely reported in the included studies. No study evaluated health-related quality of life or socioeconomic effects (such as absence from work). The studies in this review suffer from a lack of high quality evidence. Several risk of bias problems were visible such as objective measurements of outcomes without knowing the allocation of participants to the intervention groups (total or subtotal thyroidectomy) and difficulties in finding out if all planned outcomes in studies were really reported in the publications of these studies. Also, rates of outcomes (event rates) were rather low, making our estimation of the differences between the surgical techniques imprecise. Finally, all thyroidectomies were performed by experienced surgeons and it is unknown whether the described results will be the same in other settings. This plain language summary is current as of 22 June 2015.