Thyroid gland dysfunction is prevalent in older adults and may be associated with significant morbidity if misdiagnosed and left untreated. Health professionals must be conscious in this regard due to a decreased number of symptoms at presentation, an increased susceptibility to adverse events if not treated, and a greater likelihood of harm from treatment, the diagnosis and management of thyroid disorders in older adults can be challenging. (Surks & Hollowell. Age-specific distribution of serum thyrotropin and antithyroid antibodies in the US population: implications for the prevalence of subclinical hypothyroidism. J Clin Endocrinol Metabolism. 2007; 92:4575)

While some of the symptoms of hyperthyroidism and hypothyroidism in older patients are similar to those in younger patients, symptoms of both disorders often manifest in subtle ways in older patients, masquerading as diseases of the bowel or heart or a disorder of the nervous system.

In both conditions in older people there can be confusion, depression, falling, heart failure and changes in bowel habits. Not only do these signs make it difficult to distinguish hyper- from hypothyroidism in this age group, but they are also symptoms of common illnesses of older people. (Goldenberg: www.thyroid.ca/e4g.php)

The classical signs and symptoms of hyperthyroidism in the younger age group, like tremor, weight loss, palpitation, diarrhoea and heat intolerance, may be absent in the elderly (Atzmon, Barzilai, Hollowell, et al. Extreme longevity is associated with increased serum thyrotropin. J Clin Endocrinol Metabolism. 2009; 94:1251–54. [PMC free article] [PubMed] [Google Scholar) The term “apathetic thyrotoxicosis” is used to describe the symptoms of elderly hyperthyroidism who present with depression, lethargy and …)

Interpreting thyroid function tests in older adults is most of the time difficult due to age-dependent physiological changes in thyroid function, coexistent chronic illness and polypharmacy (Mariotti; Franceschi & Cossarizza, et al. The aging thyroid. Endocrinology Review. 1995; 16:686–715. [PubMed] [Google Scholar]) However, thyroid dysfunction is common in older adults and may be associated with significant morbidity if not treat symptoms of thyroid dysfunction are usually absent or may be overlooked in older patients, making the diagnosis and subsequent management challenging (Mariotti, Barbesino, & Caturegli, et al. Complex alteration of thyroid function in healthy centenarians. J Clin Endocrinol Metabolism. 1993; 77:1130–34. [PubMed] [Google Scholar]).Peeters, Debavey & Fliers, et al. Changes within the thyroid axis during critical illness. Critical Care Clin. 2006; 22:41–55. [PubMed] [Google Scholar]

Effects of Hyperthyroidism in the Elderly

Mirroring hypothyroidism, hyperthyroidism can be classified as overt, with subnormal TSH and elevated thyroid hormone, or subclinical (SCHE), with subnormal TSH and normal thyroid hormone levels. Later studies, however, showed a clear increase in the prevalence of hyperthyroidism with age, with 4–7% of subjects affected in the age groups 70 and older. Manifestations of hyperthyroidism are age-dependent, with cardiovascular symptoms more prominent in aged persons, while sympathetic symptoms prevail in the young.

It is quite clear that hyperthyroidism is associated with a multiplicity of symptoms and an increased risk of Atrial Fibrillation (AF), heart failure and osteoporosis in all age groups studied, it is typically treated in all age groups given the overwhelming clinical evidence of benefit (Flynn, Bonelli, Jung, MacDonald, Morris, & Leese: Serum thyroid-stimulating hormone concentration and morbidity from cardiovascular disease and fractures in patients on long-term thyroxine therapy. J Clin Endocrinol Metabolism 2010; 95: 186–193).

Effects of Lower Thyroid Hormone Levels in the Elderly

Hypothyroidism is characterised by reduced thyroid hormone availability both in the target tissues and the pituitary level. Hyperthyroidism is best identified by an elevation in thyroid stimulating hormone (TSH) levels to all practical effects. Overt ­hypothyroidism can be defined by an elevated TSH. Overt hypothyroidism causes significant morbidity and, probably, mortality. Although there are no evidence-based studies, there is very little controversy on the advantages of treating overt hypothyroidism Subclinical hypothyroidism (SCHO), on the other hand, is much more common. Baloch, Carayon, Conte-Devolx, Demers, Feldt-Rasmussen, et al. Guidelines Committee, National Academy of Clinical Biochemistry: Laboratory medicine practice guidelines. Laboratory support for the diagnosis and monitoring of thyroid disease. Thyroid 2003; 13: 3–126)

The above picture suggests a progressively less significant negative effect of mild hypothyroidism with aging. This may represent a shift in the balance from the effect of the atherogenic changes seen with mild hypothyroidism in the young toward potential protective effects caused by a lower metabolic rate in the elderly, but this interpretation remains hypothetical, if attractive. On the other hand, mild hyperthyroidism is clearly responsible for increasing cardiovascular morbidity. The predominant and well-established consequence is an increase in the risk of AF, but there might also be an incre ase in cardiovascular diseases (CHD).