HESX1 and pituitary stalk interruption syndrome: Although mechanical pituitary stalk rupture or pituitary stalk ischemia during breech delivery has been implicated as a major cause of PSIS, the existence of familial cases has suggested that a genetic disorder involving developmental processes underlies at least some cases of PSIS, and mutations and/or single nucleotide variants in HESX1 (MIM 601802), LHX4 (MIM 602146), PROP1 (MIM 601538), OTX2 (MIM 600037), SOX3 (MIM 313430), PROKR2 (MIM 607123), and GPR161 (MIM 612250) have been identified in patients with this condition (2, 3, 10).