<prompt> Most common cause of congenital hypothyroidism:Thyroid dysgenesisDvshormonogenesisAntithyroid antibodiesMaternal Hypothyroidism  <response>: Ref: Nelson s Textbook of Pediatrics. 19th Edition, Page: 1895.Explanation:Most cases of congenital hypothyroidism results from thyroid dysgenesisRef: NelsonThyroid DysgenesisSome form of thyroid dysgenesis aplasia, hypoplasia, or an ectopic gland is the most common cause of congenital hypothyroidism, accounting for 80-85 of cases; 15 are caused by an inborn error of thyroxine synthesis dyshormonogeneses. and 2 are the result of transplacental maternal thyrotropin-receptor blocking antibody TRBAB.In about 33 of cases of dysgenesis, even sensitive radionuclide scans can find no remnants of thyroid tissue aplasia.In the other 66 of infants, rudiments of thyroid tissue are found in an ectopic location, anyw here from the base of the tongue lingual thyroid to the normal position in the neck hypoplasia.The cause of thyroid dysgenesis is unknown in most cases.Thyroid dysgenesis occurs sporadically, but familial cases occasionally have been reported.The finding that thyroid developmental anomalies, such as thvroglossal duct cysts and hemiage- nesis. are present in 8-10 of lst-degree relatives of infants with thyroid dysgenesis supports an underlying genetic component.Causes of Congenital HypothyroidismDefect of fetal thyroid development dysgenesisAplasiaHypoplasiaEctopiaDefect in thyroid hormone synthesis dyshormonogenesisIodide transport defect: mutation in sodium- iodide symporter geneThyroid organification, or coupling defect: mutation in thyroid peroxidase geneDefects in H202 generation: mutations in DUOXA2 maturation factor or DU0X2 geneThyroglobulin synthesis defect: mutation in thyroglobulin geneDeiodination defect: mutation in DEHAL1 geneTSH unresponsivenessGsa mutation e.g.. type IA pseudohypopar-athyroidismMutation in TSH receptorDefect in thyroid hormone transport:Mutation in monocarboxylate transporter 8 MCT8 geneIodine deficiency endemic goiterMaternal antibodies:Thyrotropin receptor-blocking antibody TRBAb, also termed thvrotropin-binding inhibitor immunoglobulinMaternal medicationsIodides, amiodaronePropylthiouracil, methimazoleRadioiodine 