Hyperthyroidism in patients older than 55 years: an analysis of the etiology and management

Hyperthyroidism is a common disease in the elderly. Although some studies on the prevalence of this thyroid disorder have been performed in the aged population, several aspects of hyperthyroidism, such as etiology and treatment effectiveness, have not been fully characterized in large series of aged patients.

The aims of the present study were to determine the frequency of the diverse etiologies of hyperthyroidism, and to assess the effectiveness of therapy in adult patients older than 55 years.

We performed a descriptive, observational, cross-sectional study in the setting of a hospital endocrinology clinic. We studied a group of 313 patients with hyperthyroidism. There were 246 women (78.6%, age 67.02 +/- 8.35 years) and 67 men (21.4% age 63.34 +/- 7.63 years). Overt hyperthyroidism was diagnosed in 167 patients (53.4%) and subclinical hyperthyroidism in the remaining 146 subjects (46.6%). In every patient we studied: the etiology; presence or absence of goiter; time of evolution from diagnosis; previously and presently used treatments; current thyroid functional status (free thyroxine and thyrotropin concentrations); adequacy of disease control, and thyroid autoimmune status.

The different etiologies of hyperthyroidism were as follows: toxic multinodular goiter 43.1%; Graves' disease 21.4%; iatrogenic thyrotoxicosis 16.0%; toxic adenoma 11.8%; iodine-induced thyrotoxicosis 1.2%; subacute thyroiditis 1.0%; painless thyroiditis 0.3%; factitious thyrotoxicosis 0.3%; TSH-secreting pituitary adenoma 0.6%, and unknown etiology 3.8%. Etiology was related to age, sex, presence of goiter, degree of hyperthyroidism and autoimmune status. 77.6% of patients had been diagnosed in the last 5 years, and 91.3% in the last 10 years. Preferred therapies were thionamide drugs in patients with Graves' disease and radioiodine in patients with hyperthyroidism due to nodular disease. Surgery was performed in a limited number of patients. Periodic follow-up was used in patients with subclinical hyperthyroidism. Control of the disease was adequate in 65.3% and inadequate in 34.7% of patients who received any kind of previous therapy. In this group of patients, logistic regression analysis showed that the probability of attaining good control of hyperthyroidism was greater in patients with overt thyrotoxicosis compared to patients with subclinical thyrotoxicosis.

In patients older than 55 years, toxic multinodular goiter is the most frequent etiology of spontaneous hyperthyroidism, followed by Graves' disease and toxic adenoma. Most patients with thyroid hyperfunction can be adequately controlled, provided that effective therapy is administered. Patients with overt hyperthyroidism seem to have a higher probability of attaining adequate control of their disease than patients with subclinical hyperthyroidism, regardless of age, sex or etiology.