Hypothyroidism in older adults: A narrative review

Introduction: The prevalence of hypothyroidism increases along with aging, resulting in one of the most common comorbidities among patients over 75 years. The leading causes of hypothyroidism in older adults are iatrogenic, Hashimoto's thyroiditis, and medications. Aims: The narrative review aimed to discuss the clinical characteristics of hypothyroidism in older adults and the impact of hormonal replacement therapy on survival rates. Results: Thyroid function declines over time due to physiological changes in the thyroid stimulating hormone signaling, iodine absorption and metabolism, thyroid hormone metabolism, and activity at peripheral sites. A serum TSH value over the upper limit of the normal reference range is not necessarily attributable to hypothyroidism. However, an appropriate diagnostic work-up is required to rule out true hypothyroidism and discriminate the etiology (i.e., thyroid autoimmune diseases, iodine deficiency, drug-induced hypothyroidism). Levothyroxine treatment should be considered in cases of overt hypothyroidism. A complete risk-to-benefit assessment, particularly considering the overall health status, life expectancy, cognitive function, mood, and cardiovascular and neurological background, should be considered before treating subclinical hypothyroidism with more potential benefits in patients under 75 years old. Levothyroxine formulations facilitating hormone absorption and increasing compliance to long-term treatment should be preferred. TSH target should usually be set over 3 mIU/ml. Conclusion: Defining optimal diagnostic approaches and targeted therapeutic strategies should be considered in the personalized management of aged patients with hypothyroidism.