Graves’ disease has been identified as an independent risk factor for transient postoperative hypoparathyroidism in retrospective trials. It was confirmed by a comprehensive prospective study including 5,846 consecutive patients in 2003 . In the only existing randomized controlled trial, transient hypoparathyroidism is reported with an incidence of 28% after total thyroidectomy for Graves’ disease . The estimated prevalence is calculated with 2,000 patients per year according to the available data [2–4]. The underlying causes are complex. Preparation techniques, especially the extent of resection seem to be more influential than inadvertent parathyroidectomy [1, 5]. Postoperative hypoparathyroidism seriously affects physical health, wellbeing and quality of life. Acute hypocalcaemia can cause cramping, bronchial spasms, cardiac and digestive dysfunction and can therefore be life threatening. Long-term effects result in cataract, conjunctivitis, pruritus, osteopenia, calcifications of the basal ganglia (Fahr’s syndrome), neurological and psychic impairments. Despite calcium and vitamin D substitution, wellbeing is predominantly impaired by anxious and phobic psychological disorders . Care and treatment costs as well as the status of employee’s illness are therefore of economic relevance.
At present, total thyroidectomy is favored for definite surgery in Graves’ disease instead of subtotal resection, according to the national S2-guideline issued by the Work Group of the Scientific Medical Professional Societies (AWMF) . The current evidence supporting a total thyroidectomy in Graves’ disease is based on two randomized controlled trials [2, 8], one meta-analysis  and four retrospective trials [10–13]. All studies evaluate the outcome after total versus subtotal thyroidectomy, in relation to the incidence of recurrent disease. The meta-analysis, cited in the national S2-guideline, displayed a zero-recurrence rate and an equal risk of method-associated complications . However, the corresponding Cochrane diagnostic review commentary emphasizes group inhomogeneity as a substantial methodological deficit. Four retrospective trials [10–13] demonstrated a significantly lower incidence of transient hypoparathyroidism after subtotal, compared to total resections, while the incidence of recurrent disease differed according to variable sizes of the remnants (mean 6.1 g, range 1 to 12 g) and follow-up periods. Among these four trials only one clearly defined the size of the remnant with a unilateral residual thyroid tissue of ≤ 2 g when a subtotal resection was performed . With this measure, the incidence of hypoparathyroidism significantly decreased, while the incidence of recurrent disease remained unaltered within a median follow-up of 6.7 years. The recurrence rate of 0.5% in this study was attributable to inadvertently spared pyramidal lobes in all patients as the result of a systematic default. Two prospective randomized controlled trials by Witte et al., 2000  and Barczynski et al., 2012  again aimed at recurrence of Graves’ disease as the primary endpoint, addressing different remaining tissue volumes and resection techniques. The trial by Witte et al. compared two interventional arms: one arm comprised a unilateral total resection and a contralateral subtotal resection with a remaining remnant of ≤ 4 g; the second arm comprised a bilateral subtotal resection with a remaining remnant of ≤ 4 g in total to the control arm total thyroidectomy. Barczynski et al. considered bilateral remnants of approximately 2 g on each side. Both trials displayed a significantly lower incidence of transient hypoparathyroidism in the intervention groups. While the incidence of recurrent disease was not significant, clinically not relevant, and detectable in all affected patients six months after surgery, after a follow up of 18 to 58 months in the trial by Witte et al., Barczynski et al. reported significantly higher relapse rates within 60 months follow up. Endocrine orbitopathy did not worsen after subtotal resection in both trials. So far, the evidence from the prospective randomized controlled trials seems contradictory regarding the incidence of clinically relevant recurrent disease. Moreover, the S2-recommendation lacks appropriate evidence in view of comorbidities. According to our knowledge, the incidence of transient hypoparathyroidism has never been valued as primary endpoint. Current data suggest a relevant reduction of the incidence of transient hypoparathyroidism after a near-total resection if defined remnants of ≤ 1 g on each side are left around the posterior suspensory ligament of Berry (Ligamentum thryoihyoideum laterale). The resection will be safe compared to standard total thyroidectomy regarding recurrent disease, endocrine orbitopathy and method associated complications [2, 9, 13]. A prospective randomized controlled trial is necessary to define the gold standard resection for the surgical therapy of Graves’ disease in view of patients’ safety and quality of health care.