Table 1 Characteristics of studies selected for estimation of prevalence of GO

Abraham-Nordling et al. [18]

3.5 million general population

Sweden

2003–2005

Prospective, population registry-based, reporting on incidence of Graves’ hyperthyroidism and all grades of severity of GO

Zaletel et al. [19]

1.0 million general population

Slovenia

1999–2009

Single institution, prospective cohort study of patients with thyroid disease, including Graves’ hyperthyroidism as a subgroup

Laurberg et al. [20]

0.5 million general population

Denmark

1992–2011

Single institution, prospective cohort study, reporting on incidence of moderate-to- severe GO