The epidemiology of endocrine tumours.

The epidemiological study of disease aims to increase our understanding of the aetiology, patterns of occurrence and natural history of clinical conditions by reference to populations and defined sub-populations. One of the potential gains from such an approach is the possibility of drawing inferences regarding the contributions of genetic and specific environmental factors in causation. On a more immediately practical level, the determination of prevalence of disease in defined populations is important for the planning of specialist facilities and the prediction of direct and indirect costs of treatment. Tumours of endocrine glands, although rare in the context of the overall burden of oncological disease, have provided important insights into the mechanisms of sporadic and familial tumour formation, important examples being the primary role of constitutively activated cell membrane G protein-linked mechanisms in determining proliferation in pituitary somatotroph adenomas (Spada et al. 1990), and the recent elucidation of the molecular basis of the multiple endocrine neoplasia (MEN) syndromes (Ponder 1994, Chandrasekharappa et al. 1997). However, it is often difficult to obtain an epidemiological perspective for endocrine tumours, either because of asymptomatic disease which results in incomplete case ascertainment or the rarity of individual tumours (Table 1). The reported incidence of parathyroid adenoma is a classical example of the dependence of incidence data on diagnostic facilities and local policies for routine serum calcium measurements. These problems are magnified by the fact that clinical care of endocrine tumours may occur in a variety of settings (including endocrinology,