A permanent thyroid deficiency that is present from birth, characterized by low levels of thyroid hormones caused by disorders in the development or function of the pituitary. The clinical manifestations can be subtle, probably as a result of trans-placental passage of some maternal thyroid hormone or due to the fact that many infants have some thyroid production of their own. Goiter is always absent. Slow linear growth and developmental delay are usually apparent by 4-6 months of age. Without treatment hypothyroidism results in severe intellectual deficit and short stature. The hypothyroidism is caused by mutations in genes regulating pituitary gland development including HESX1, LHX3, LHX4, POU1F1 and PROP1 (3p21.2-p21.1, 9q34.3, 1q25, 3p11 and 5q).