It was. Cretinism was one of the manifestations of iodine deficiency. The trope of crétin des Alpes (lit. cretin from the Alps) existed for a reason. The manifestation was goitres and stunted development, with people who seemingly stopped growing up around 14. Pretty much the story’s subject. It was a public health problem before iodised salt.

https://en.m.wikipedia.org/wiki/Congenital_iodine_deficiency...