Endocrine Abstracts

The aetiology of thyroid nodules is due to the interaction between genetic and environmental factors. Thyroid nodules are common. Epidemiological studies suggest that 1% of men and 5% of women have thyroid nodules detected clinically and that the frequency increases with age and in iodine-deficient populations. With the increasing use of sensitive imaging techniques, an increasing proportion of thyroid nodules are detected incidentally. Up to 50% of nodules >1 cm detected by ultrasound are undetected by clinical examination. Autopsy and prospective ultrasound studies in the US detected asymptomatic nodules in 50 and 67% respectively. Many nodules are detected because of their size or anterior position in the neck, or the skill of the physician performing the examination but most thyroid nodules will not be clinically recognised. Although thyroid nodules are common, thyroid cancers are rare. The annual incidence quoted of all thyroid cancer ranges between 1 and 10 per 100 000 population in most countries and is two to four times as frequent in women as men. Recently reports have suggested an increase in thyroid cancer incidence which is only partly explained by an increased detection of small papillary thyroid cancers. Clinically silent papillary microcarcinomas (diameter <1 cm) have been reported in up to 36% of adults at post-mortem in population-based studies. A comparison of these papillary micorcarcinoma incidence rates in autopsy studies with the incidence rates for clinically apparent papillary carcinomas strongly suggests that most papillary microcarcinomas will not lead to clinically apparent thyroid carcinomas. Therefore the challenge in the management of nodular thyroid disease is to identify those few nodules that are malignant when the vast majority of thyroid nodules, which are so common in the population, are benign. This requires a rational evidence-based strategy for the differential diagnosis, risk stratification, treatment and follow-up.