CRETINISM

CRETINISM was the first well-recognised clinical form of mental defect. It was also one of the earliest well-defined metabolic errors to be recognised. It remains the classical example of disease produced by endocrine anomaly. Therapeutically also, cretinism has made history as being the first metabolic and hormonal disorder responsible for mental retardation to respond to specific treatment. Despite acentury and a half of attention the syndrome remains an imprecise concept with much still to be explained. Many cases previously described as cretins would not now be accepted as such; this applies to cases of Down’s syndrome which were once described as furfuraceous (scaly, scurfy) cretins. It is now clear that cretinism as an expression of thyroid defect can have a number of different causes. Some recent developments in diagnosis and therapy have been summarised by BLIZZARD and COON.* Recognition of the complicated chain of metabolic events which occurs in the thyroid makes it clear that interruption at different links in the chain will produce different syndromes, perhaps requiring different treatment. Firstly, an enzyme defect may prevent the synthesis of normal amounts of thyroid hormone and result in a hypothyroid patient with a hyperplastic thyroid gland avid for iodide-i.e., a congenital goitrous cretin. In fact not all such metabolic defects result in congenital goitre, though this may appear later, as may the evidence of hypothyroidism. Secondly, cretinism may be due to a partial or complete anatomical deJiciency of the thyroid gland. Lingual or incompletely descended thyroids fall into this category, since they are functionally inactive. In most cases the cause of the failure of thyroid development is unknown, but BLIZZARD and others3 showed that in a minority it may be due to the formation of thyroid antibodies in the mother during pregnancy; they found thyroid antibodies in the serum of 26 per cent of the mothers of 121 athyrotic cretins, compared with 5 per cent of control pregnant women. In a third group, the mother has been treated with drugs of the thiouracil type,s with large doses of iodideY2 or with other substances which interfere with thyroid metabolism during pregnancy. The infant’s thyroid defect is usually transient, but if the defect is not speedily recognised and treated permanent mental defect may result. Then there is a fourth group where endemic cretinism is due to defective maternal intake of iodine. South-eastern France, North-western India and the Great Lakes of North America are classical iodine-deficient areas with a high incidence of adult goitre, but whether they also had a high incidence of cretinism seems less clear, and in North America the situation has been changed by the addition of iodine to the table-salt. Despite the diversity of possible causes, cretinism is a rare disease-thus, in one series of 1,900 children with severe mental defect1 only 2 cases were diagnosed. This fact suggests, in Britain at any rate, that any single cause operates very infrequently. MCGIRR and HUT-