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This chapter addresses the following Geriatric Fellowship Curriculum Milestone: #18
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Learning Objectives
Understand age-related changes in thyroid function and structure.
Recognize the symptoms of thyroid dysfunction in older people.
Interpret thyroid function tests in the context of concurrent medication use and illness.
Describe the evaluation and treatment of thyroid disease in older people.
Identify thyroid nodules that require evaluation via fine-needle aspiration (FNA).
Summarize therapy for papillary thyroid carcinoma in older people.
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Key Clinical Points
Aside from a slight increase in thyroid-stimulating hormone (TSH) with age, changes in thyroid function and structure are not considered normal aging and require assessment of medications or conditions that affect thyroid function and investigation for thyroid disease.
Overt hyperthyroidism and overt hypothyroidism may be difficult to recognize in older people and always require treatment.
Treatment should be considered for subclinical hyperthyroidism in older people and for patients with subclinical hypothyroidism who have higher concentrations of TSH.
The evaluation of thyroid nodules does not differ with age. Any nodule meeting criteria should undergo FNA, preferably with ultrasound guidance.
Papillary thyroid carcinoma is the most common thyroid cancer and may be more aggressive in older people. Thyroidectomy should be performed, and additional management should be tailored to the health status of the individual.
Anaplastic thyroid carcinoma presents almost exclusively in older people and has a poor prognosis.
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Thyroid hormone has widespread systemic effects and plays a critical role in metabolism at all ages. Both excess and deficiency can have severe physiologic consequences, even leading to death. The hypothalamic-pituitary-thyroid axis ensures tight regulation of thyroid hormone concentrations, even in advanced age. In addition, the thyroid gland has evolved to have sufficient redundancy so that only a minority of the gland is required for normal thyroid function. Nevertheless, the prevalence of all forms of thyroid disease, both functional and structural, increases in older people. An astute clinician is required, as recognition and management are more challenging in this age group.
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CHANGES IN THYROID FUNCTION WITH AGE
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The thyroid gland produces two thyroid hormones, thyroxine (T4) and triiodothyronine (T3), which differ only in the number of iodines (Figure 109-1). T4 is the major hormone secreted by the thyroid gland, at an amount that is 11 times the secretion of T3. Additional T3 is produced peripherally by deiodination of T4 in the liver, kidney, and brain. Within the cell, T3 is the more potent hormone, binding to thyroid hormone receptors with higher affinity. However, because T4 levels act as a reservoir of thyroid hormone, with a longer half-life and circulating concentrations 100 times higher than T3, T4 concentrations are more commonly measured in the clinical setting.
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