In GSDIa, the G6P excess in ER (due to G6Pase deficiency) has been associated to increased 11βHSD1 activity, while in GSDIb the lack of G6P in ER (due to G6PT deficiency) has been associated to decreased 11βHSD1 activity [17]. Here, G6PC1 is linked to hyperinsulinemic hypoglycemia, familial, 4.