Congenital Hypothyroidism is a rare but serious malformative pathology, subject to congenital screening in several countries around the world. its impact once omitted is serious and irreversible. The form with agenesis of the thyroid gland called athyreosis can be associated with several malformations, cardiac, renal or skeletal. Patients living with athyreosis most often have symptoms of chronic hypothyroidism, which can be attributed either to a FT3/F4 ratio that is too low or a defect in the peripheral deiodation of T4 to T3. We report the case of a young girl with athyreosis who maintains a refractory hypothyroidism syndrome.