Cancer of the thyroid (ICD-9 193)

The incidence of thyroid cancer in Iceland was much higher (males 59/10⁶, females 88/10⁶) than in any other country. Only women in some parts of Finland and Norway reach the same level as the Icelanders. The mortality was low everywhere; in Germany the mortality increased towards the south and approached the Icelandic level.

The mortality/incidence ratios were lowest in the Nordic countries except Denmark, and highest in Poland.

The incidence of thyroid cancer increased slowly with age, the Icelanders having the highest rates in all age groups.

Ionizing radiation is known to increase the risk of thyroid cancer, but that is not likely to explain the observed spatial variation. High dietary iodine intake is suggestive for a higher risk of papillary carcinoma which is the dominating type of thyroid cancer in the Nordic countries. This may partly explain the higher risk in Iceland and coastal Norway. Iodine deficiency areas with endemic goiter typically show an increased risk of thyroid cancer. Such areas are seen in this Atlas in the mountains of southern Germany and Poland. The most important factor behind the regional variation, however, is the varying level of diagnostic activity.