Inborn errors of thyroid hormone biosynthesis.

Permanent congenital hypothyroidism in the Netherlands (incidence 1:3000) is caused for 70-80% by a- or dysgenesis of the thyroid gland, for about 15% by dyshormonogenesis and for 10-15% by hypothalamic-pituitary disturbances. The heredity of congenital hypothyroidism caused by dyshormonogenesis is mendelian in character and follows, with a few exceptions, an autosomal recessive pattern. The diagnosis of these inborn errors is based on a combination of imaging studies, plasma hormone and thyroglobulin concentrations, and the concentration of iodide and iodinated peptides in the urine. The contribution of molecular biology is becoming an important factor in the classification of hereditary congenital hypothyroidism.