Thyroid disease and its treatment: short- and long-term consequences.

Thyroid dysfunction is common, with up to 5% of the population affected by hyper- or hypothyroidism. Short-term effects of overt thyroid dysfunction are well recognised: for example, effects of hyperthyroidism on pulse rate or blood pressure and effects of hypothyroidism on lipids. There is now also increasing evidence for long-term morbidity and mortality associated with thyroid dysfunction. This includes an increased likelihood of cardiovascular and cerebrovascular mortality in subjects with previous thyrotoxicosis treated with radioiodine, and of osteoporotic fracture of the femur in those with previous thyrotoxicosis. Subclinical or mild thyroid dysfunction may also be associated with long-term effects, with evidence for increased risk of atrial fibrillation in those with subclinical hyperthyroidism. Treatment for thyroid disease may also cause long-term problems. The cancer risk associated with therapeutic radioiodine for hyperthyroidism has been investigated extensively. Our own studies reveal no increase in cancer diagnoses or deaths, apart from a small increase in thyroid cancer risk which may be associated with the underlying thyroid disease.