Inadequate thyroid hormone production in newborn neonates is known as congenital hypothyroidism (CH). It can be caused by a thyroid gland anatomical anomaly, a thyroid metabolism inborn error, or iodine shortage. Thyroid hormone plays a crucial function in brain development during the first 2-3 years of life. Mental retardation is the most prevalent preventable cause of congenital hypothyroidism. It is the most frequent illnesses in neonates that are associated to mental impairment and growth retardation. If an error in thyroid gland development or a problem in thyroid hormonogenesis is left untreated for several months, it might result in growth failure, permanent dysfunction, or irreversible intellectual disability. In other situations, the altered neonatal thyroid function is only temporary, due to maternal medicine passing across the placenta, maternal blocking antibodies, or iodine deficit or excess.