Endocrine Abstracts

Subclinical thyrotoxicosis, due to endogenous hyperthyroidism, affects about 1% of the older population and is predominantly caused by indolent progression to a state of autonomous thyroid function in people with nodular thyroid disease. For more than a decade, it has been known that subclinical hyperthyroidism is associated with a three-fold increased risk of atrial fibrillation (Sawin et al.) over 10 years of follow-up. More recently, three separate observational studies of community-dwelling populations, totaling 5,023 subjects, have shown that subclinical hyperthyroidism is associated with an increased all-cause or vascular disease mortality (Parle et al., Guselkoo et al., Cappola et al.). In addition, there is accumulating evidence that subclinical hyperthyroidism is associated with a low BMD, increased fracture risk and dementia. Whether individuals with subclinical hyperthyroidism warrant treatment for their thyrotoxicosis on prognostic grounds remains unknown, but this is certainly an accepted indication for treatment in some healthcare environments. Sixty six percent of North American clinical thyroidologists responded that they would treat an elderly woman with subclinical hyperthyroidism, two thirds selecting radioiodine therapy (McDermott et al.). However, as it is clear these individuals are at increased vascular risk, clinicians need also to consider whether conventional vascular risk factor interventions including, aspirin, statins and tight blood pressure control represent optimal therapies for these ‘at risk’ individuals. Although betablockers are falling out of favour as first-line antihypertensives in most circumstances, their specific cardioprotective effects against thyroid hormones also make them a very logical therapeutic choice for individuals with subclinical hyperthyroidism. I believe that until more outcome data is available, all patients with subclinical hyperthyroidism should be treated, some with specific antithyroid treatments, others with conventional risk-factor management.