Neonatal screening for congenital hypothyroidism can detect permanent and transient hypothyroidism. The latter condition is called neonatal transient hypothyroidism. This may result from various causes, but, especially, it should be suspected whenever there is a history of maternal autoimmune thyroid disease, including Hashimoto thyroiditis, Graves disease, hypothyroidism on replacement therapy, or recurrent congenital hypothyroidism of a transient nature in subsequent siblings. Transplacental TSH-receptor antibodies may affect fetal or neonatal thyroid function. Although thyroid dysfunction may be transitory, long-term follow-up is desirable.