Same-sex twins have a high incidence of congenital hypothyroidism and a high probability to be missed at newborn screening.

•Incidence of CH in same-sex twins is much higher than that in general population.•Distinguishing same-sex twins and different-sex twins is more feasible in screening.•In cases with a positive result in a same-sex twin, the other one should be recall.•Specific screening guidelines should be evaluated for all same-sex twins.