Global epidemiology of hyperthyroidism and hypothyroidism

Key Points Thyroid disease is a global health problem that can substantially impact well-being, particularly in pregnancy and childhood. In advanced economies, the prevalence of undiagnosed thyroid disease is falling owing to widespread thyroid function testing and relatively low thresholds for treatment initiation. Iodine nutrition remains a key determinant of thyroid function worldwide, and continued vigilance against the resurgence of iodine deficiency in previously sufficient regions remains essential. More studies are needed in developing countries, especially within Africa, to understand the role of ethnicity and iodine nutrition fluxes in current disease trends. Iodine nutrition is a key determinant of thyroid disease risk, and continued vigilance against iodine deficiency remains essential. Here, Peter Taylor and colleagues review the global incidence and prevalence of thyroid disease, highlighting geographical differences and the effect of environmental factors, such as iodine supplementation, on these data. Thyroid hormones are essential for growth, neuronal development, reproduction and regulation of energy metabolism. Hypothyroidism and hyperthyroidism are common conditions with potentially devastating health consequences that affect all populations worldwide. Iodine nutrition is a key determinant of thyroid disease risk; however, other factors, such as ageing, smoking status, genetic susceptibility, ethnicity, endocrine disruptors and the advent of novel therapeutics, including immune checkpoint inhibitors, also influence thyroid disease epidemiology. In the developed world, the prevalence of undiagnosed thyroid disease is likely falling owing to widespread thyroid function testing and relatively low thresholds for treatment initiation. However, continued vigilance against iodine deficiency remains essential in developed countries, particularly in Europe. In this report, we review the global incidence and prevalence of hyperthyroidism and hypothyroidism, highlighting geographical differences and the effect of environmental factors, such as iodine supplementation, on these data. We also highlight the pressing need for detailed epidemiological surveys of thyroid dysfunction and iodine status in developing countries.