Congenital hypothyroidism. X-ray of the skull of a 6 month old infant showing an open anterior fontanelle with large sutures. Growth is also stunted, suggesting that the infant has congenital (present from birth) hypothyroidisma. This is a deficiency of thyroid hormone caused by the underactivity of the thyroid gland. If left untreated hypothyroidism can lead to dwarfism, mental retardation and dry puffy skin. Treatment is with supplements of the thyroid hormone thyroxine.