Furthermore, PVN CRH synthesis and secretion are stimulated by NPY, the synthesis and secretion of which in turn is stimulated by elevated corticosteroid levels, as well as by norepinephrine from the brain stem (see ref. [155] for review of PVN NPY and CRH interactions potentiating elevated SNS tone, increased HPA axis activity, and metabolic syndrome). Here, CRH is linked to metabolic syndrome.