In premenopausal women, exercise training is commonly associated with menstrual disturbances, including functional hypothalamic amenorrhea (FHA).  FHA is characterised by chronic estrogen deficiency similar to that observed in postmenopausal women.  Despite being young and otherwise healthy, exercise trained women with FHA (ExFHA) demonstrate impaired endothelial function, increased regional vascular resistance, and decreased regional blood flow.  Estrogen deficiency is thought to play an important role.  Accordingly, similar findings have been reported in postmenopausal women.  However, in contrast to postmenopausal women, ExFHA women demonstrate low, rather than elevated, resting arterial blood pressure.  In postmenopausal women, estrogen deficiency due to menopause is assosciated with both increased sympathetic nervous system activity and augmented activation of the renin-angiotensin system.  Our investigations of blood pressure regulation in young premenopausal women with ExFHA, compared with age- fitness- and body mass-matched eumenorrheic women, identified augmented lower limb skeletal muscle sympathetic nerve activity (MSNA) yet lower arterial blood pressure during simulated orthostatic stress using lower body negative pressure (LBNP). Further, in ExFHA, non-activation of the renin-angiotensin system despite increasing LBNP (0, 10, 20 and 40 mmHg) was also observed. Thus, otherwise healthy ExFHA women demonstrate low arterial blood pressure and disruption of the normal circulatory response to an orthostatic challenge: namely plasma renin, angiotensin II and aldosterone fail to increase and blood pressure is defended by augmented sympathetic vasoconstrictor responses. This invited talk will examine what is known about the uncoupling of the reflex sympatho-neural and renin-angiotensin system responses to a hypotensive stimulus in estrogen deficient physically active premenopausal women with FHA.