Prop1 is necessary to activate expression of Pou1f1 (*173110) (Sornson et al., 1996), and POU1F1 is mutated in individuals with CPHD or IGHD (Radovick et al., 1992; Sobrier et al., 2016; Tatsumi et al., 1992; Turton, Reynaud, et al., 2005; Turton, Strom, Langham, Dattani, & Le Tissier, 2012) and no other clinical features. This evidence concerns the gene POU1F1 and isolated congenital growth hormone deficiency.