BDNF and hyperinsulinemic hypoglycemia, familial, 4: Previous studies have shown that hippocampal BDNF induction by EET (or exercise) is larger in males76, 77 or females,78 or similar between genders.79 The reasons of these mixed results are unknown, but could be because hippocampal BDNF levels are affected by estrous cycle and sex hormones.80, 81, 82 We did not observe any gender-specific differences in BDNF levels in either genotype or in BDNF induction by EET; the gender effect may be relatively smaller than the genotype effect (BDNF deficiency) and age-dependent environmental (EET) effect.