BDNF deficiency due to epigenetic alterations has been linked to a plethora of psychiatric diseases, suggesting that the lack of BDNF is a central biomarker for such disorders (Corominas-Roso et al., 2013; Janke et al., 2015; Jha et al., 2016). Here, BDNF is linked to hyperinsulinemic hypoglycemia, familial, 4.