SUBCLINICAL THYROID-DYSFUNCTION IN THE ELDERLY

Subclinical thyroid dysfunction is more common in older persons. By de finition, these disorders are recognized by isolated elevation or supp ression of the serum TSH concentration, in association with a normal s erum free thyroxine level. Among individuals over 65 years old, subcli nical hypothyroidism is found in similar to 10% of women and similar t o 3% of men. It is most commonly due to autoimmune thyroiditis or prev ious treatment for hyperthyroidism. There may be three indications for L-thyroxine therapy: (a) presence of antithyroid antibodies, indicati ng substantial risk of progression to over hypothyroidism; (b) symptom s consistent with thyroid hormone deficiency; and (c) an elevated seru m LDL-cholesterol Subclinical hyperthyroidism is present in similar to 1%-2% of older persons. The most common cause is excessive thyroid ho rmone therapy, followed by mild endogenous hyperthyroidism due to Grav es' disease or nodular goiter. These can be differentiated from other causes of low serum TSH concentration based on clinical and other labo ratory and radionuclide scan criteria. The most serious consequences o f subclinical hyperthyroidism are atrial fibrillation and osteoporosis , to which elderly patients are particularly predisposed.