Two molecular scientists from Zurich wrote this paper as a systematic review, asking the question of whether dietary iodine intake is a risk factor for developing thyroid cancer later on life. They speculate that low iodine intake is a risk factor, and this was shown in animal models.
The paper elegantly describes a theory of low iodine, high thyroid stimulating hormone and enlarged glands, with resultant increase in tumours and of follicular adenocarcinomas. Where this study comes unstuck is the analysis of human populations. Several confounding factors skew any long-term retrospective study between iodine intake and thyroid cancer. The authors rightly recognise the increasingly important role of early detection and surgery over time making analysis difficult. A weak link is shown between countries’ thyroid death rates and iodine intake in women. But they acknowledge that retrospectively assessing an individual lifetime intake of iodine is an inexact science. This paper aims to answer the question of iodine and thyroid cancer, but is so wide ranging it leaves many more questions unanswered.