Congenital hypothyroidism (CH) is a rare disease that affects 1 in 3500 newborn. This condition is detected consistently since the late 1970s in France, which has enabled early care and a significant improvement of the intellectual stature and prognosis of these children. However neurodevelopmental disorders persist in 10-15% of cases. More associated pathologies have been reported in nearly 10% of cases. These observations are in most cases poorly understood. The family nature of the HC is now well accepted and a dozen genes is now involved. However in the majority of cases (HC not due to a disorder of the organification of iodine), few mutations have been found relative to the number of patients (5-10%), suggesting the involvement of other genes. Some of the genes have been implicated in such specific syndromic forms but many pathological associations remain unexplained. Also, a more complete elucidation of genetic HC enable a better understanding of its etiology and thus share the risk of familial recurrence (frequently asked by parents of children with questions) and secondly the presence of comorbidities.