FKBP5 and Cushing syndrome: NR3C1 and FKBP5, the genes that encode the glucocorticoid receptor and FK506 binding protein (which regulates glucocorticoid receptor sensitivity), are both involved in cortisol signalling and were selected in studies investigating stress response or stress related neuropsychiatric conditions such as PTSD or MDD, or in Cushing’s Syndrome where cortisol is known to be dysregulated.