Because the presence of medullary thyroid cancer in multiple endocrine neoplasia type 2 (MEN2) syndrome might involve screening of families, in order to evaluate the presence of thyroid nodules, proto-oncogene RET mutations, and serologic calcitonin values, we considered that the respective epidemiology was in fact influenced by direct medical intervention. This evidence concerns the gene RET and medullary thyroid gland carcinoma.