Congenital hypothyroidism (CH) comprises a variety of disorders of either the thyroid gland (CH-T) itself or the regulatory system stimulating the thyroid gland consisting of the hypothalamus and the pituitary gland (central congenital hypothyroidism, CH-C), which both result in a lack of thyroid hormone (TH) in the neonatal period. Here, TH is linked to cyclic hematopoiesis.