In the case of congenital hypothyroidism, your blood levels of thyroid hormone are too low at the time of your birth. The problem usually lies with the thyroid gland itself. Perhaps it did not form at all or did not form properly, or perhaps it did not migrate to the normal location or does not synthesize any hormone (dyshormonogenesis). We call this condition congenital hypothyroidism of thyroidal origin or CH-T.
You can also have a thyroid hormone deficiency because your hypothalamus or pituitary does not function properly, and the thyroid gland is not properly controlled. We call this congenital hypothyroidism of central origin or CH-C. This is the case in approximately 10% of newborns with congenital hypothyroidism.
Sometimes a newborn has too little thyroid hormone because substances in the mother's uterus were passed on to the child. For example, if the mother uses thyroid-suppressant medicines, has thyroid disease or has an excess or a deficiency of iodine. This type of CH is called transient CH.