The brain continues growing for 2-3 years after birth, for which thyroid hormones are critical. If a newborn's thyroid doesn't work normally for any reason - not formed properly (called dysgenesis) or cannot function properly (dyshormonogenesis), then the brain and body do not get enough hormone (hypothyroidism) and cannot grow normally.

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In womb, the mother's thyroid hormones may help, but after birth the deficiency is disastrous, causing loss of 5 IQ points every month of life. The result - permanent mental retardation!

On World Thyroid Day, IANSlife spoke to Dr Anju Virmani, Senior Consultant Endocrinologist, Madhukar Rainbow Children's Hospital, with over three decades of experience to know more about thyroid disorder in children. She says, "The difficulty is the baby usually seems normal at birth; by the time problems are noticed, the irreversible damage can be quite severe. Every single baby must have a TSH test at birth."

"If hypothyroidism occurs in older children, the ill effects are easier to reverse if detected in time. Hypothyroidism stunts brain development, physical growth, and puberty. In the most severe form - a cretin - is a short, dull, slow, heavy child, with a pale puffy face, hoarse voice, doughy skin, tired and lethargic; maybe constipated, maybe with a neck swelling. Usually all the signs and symptoms are not present - it has to be suspected and tested for. Children with autoimmune diseases like diabetes and wheat allergy are more prone to hypothyroidism, and need regular testing," Dr Virmani points out.

She adds, "Hyperthyroidism, rare in children, is the opposite. The child is hungry but losing weight, hot, sweaty, irritable, hyperactive, anxious, unable to concentrate; with prominent eyes. Diagnosing is easy, but the treatment is more complicated. Hyper or hypo, school performance suffers."

So, what are the take home messages? She replies, "Please remember that everyone deserves a thyroid test at birth, with early treatment if needed. In older children and adolescents, if there are any suggestive symptoms as briefly listed above, think of the thyroid - easy to test for, easy to diagnose, easy to treat! Why be a cretin?"