Congenital hypothyroidism ( Cretinism)

Hypothyroidism usually appears as either congenital/from birth or acquired in children.  Acquired hypothyroidism is an under activity of thyroid gland in later childhood. It occurs from a condition in which the body attacks its own tissues. When the thyroid gland gradually stops working eventually it may cause acquired hypothyroidism. This first sign of acquired hypothyroidism is growth deceleration. Children may develop constipation, cold intolerance and decreased energy. Puberty may be very slow, late or absent. There are gradual changes in facial appearance, face appears pale and puffy. Other changes include a slow heart rate, some hair loss and slow reflexes.

On the contrary, congenital hypothyroidism also aka cretinism is an under activity of the thyroid gland at birth. When the thyroid gland is poorly developed or absent it causes thyroid hormone deficiency. As a result, thyroxine the main hormone produced by thyroid gland is not produced and a condition develops called as congenital hypothyroidism. Cretinism causes growth retardation, developmental delay and other abnormal features. Congenital hypothyroidism is twice as common in females. This condition is present from birth therefore it is likely to pass in families.

Cretinism is also caused due to dietary iodine deficiency in mothers during pregnancy. In areas of severe iodine deficiency, low concentration of thyroxine in the blood (hypothyroxinemia) can cause cretinism in both mother and fetus. The iodine deficient diets affect the developing fetus, newborn and the young children. In low iodine areas cretinism is a major cause of preventable intellectual impairment in children. Thus, to prevent irreversible damage iodine should be given before conception or early in pregnancy.

The symptoms of congenital hypothyroidism appear gradually. The clinical features depend upon thyroid hormone deficiency and age of the patient. The clinical features are not characteristic at birth. During the neonatal period the earliest sign may be prolonged physiological jaundice.  The other features present are poor/difficult feeding, noisy breathing, little cry and much sleep. The abdomen is large with an umbilical hernia.

The full clinical presentation develops by 3-6 months. The appearance becomes apathetic, infantile and unconcerned with the surrounding. The milestone of development is delayed resulting in short stature. The ratio of upper segment to lower segment is large due to short legs. The forehead appears wrinkled, while the tongue is broad and protruded keeping the mouth open. The neck appears short and thick, while the hands and legs are broad and stumpy. The muscle tone is decreased, slow relaxation of ankle jerk is observed.

The laboratory investigation consists of checking serum T4 level, TSH level. Most case of congenital hypothyroidism is detected by newborn screening tests. The radiograph detects any retardation of osseous development. Thyroid scans or radio labeled iodine detect absence of thyroid tissue. The thyroid hormone replacement treatment will be for lifetime. The thyroxine used for therapy however, should not be mixed with iron or any formula containing iron or soy.

References: Davidson's principles and practice of medicine, 18th edition