A high rate of undiagnosed hypoglycemia has been previously noted in reports of dominant congenital HI, including mutations of the KATP channel, as well as in HI due to dominant activating mutations of glucokinase (Christesen et al., 2002; Dullaart, Hoogenberg, Rouwe, & Stulp, 2004; Glaser et al., 1998; Gloyn et al., 2003; Wabitsch et al., 2007) and glutamate dehydrogenase (Stanley et al., 1998) and in a family with HI associated with the hexokinase‐1 locus (Pinney et al., 2013). Here, GCK is linked to Hypoglycemia.