Thyroid dysfunction in ageing populations.

The world population is ageing. According to projections of the World Health Organisation, it is expected that between 2020 and 2050, the number of people aged 60 years and older will double to reach 2.1 billion worldwide, while the number of persons aged 80 years or older is expected to triple to reach 426 million worldwide. Thyroid dysfunction is common in older populations and comes with specific challenges regarding its diagnosis and management. In older populations, overt hypothyroidism and hyperthyroidism often present differently and with fewer symptoms. This may be due to confounding by the higher presence of comorbidities and polypharmacy, but also because of age-related differences in underlying disease aetiology. While autoimmunity remains the main cause of thyroid disease in older populations, thyroid autonomy contributes significantly to hyperthyroidism in older populations. The serum TSH distribution displays a shift toward higher concentrations in older populations, resulting in a higher prevalence of (biochemically defined) subclinical hypothyroidism. Concurrently, age-related differences in body composition and physiology may cause changes in the absorption, distribution, and clearance of drugs, resulting in slower drug metabolism. Management of thyroid dysfunction in older populations requires careful diagnosis, gradual treatment, and lifelong follow-up, as older people are at increased risk of undertreatment and overtreatment.