Transient neonatal diabetes mellitus (TNDM) is a developmental disorder of insulin production that resolves postnatally within the first year of life. Intrauterine growth restriction is usually present. TNDM infants develop diabetes in the first few weeks of life but may go into remission in a few months, with possible relapse to a permanent diabetes state usually around adolescence or as adults. The pancreatic dysfunction in this condition may be maintained throughout life, with relapse initiated at times of metabolic stress such as puberty or pregnancy.