Selenium and seleno dependent glutathione peroxidase (GPX) deficiency has been described in endemias of myxedematous cretinism. In northern Zaire, a selenium supplementation trial has been conducted. Beside correcting the GPX activity, two months of selenium supplementation was shown to modify the serum thyroid hormones parameters in clinically euthyroid subjects and to induce a dramatic fall of the already impaired thyroid function in clinically hypothyroid subjects. These results further support a role of selenium in thyroid hormone metabolism. In an iodine deficient area, this selenium deficiency could lead to opposite clinical consequences: protect the general population and the fetus against iodine deficiency and brain damage; and in turn, favour the degenerative process of the thyroid gland leading to myxoedematous cretinism.

Deiodinase type I which has been shown to be a seleno-enzyme could account for the changes in thyroid hormones in our subjects. Our data show that selenium plays a definite role in thyroid hormone metabolism in humans. Selenium could be an important cofactor in the clinical picture of iodine deficiency in Central Africa and could be involved in the aetiology of both forms of cretinism.