Most Common Preventable cause of Mental retardation is Hypothyroidism.
Clinical scenario : Child with Hypotonia , Umblical hernia and prolonged physical Jaundice
Sutures - Widely open
Posterior fontanel - Open in hypothyroidism
Important point : TSH in child should be done >48hrs - 6days.
If maternal TSH is high then we get false positive high TSH in Cord blood as well as on day 1.
i.e 24-48hrs in the child - Normally there would be High TSH.