Our key findings were as follows: (1) Postmenopausal women demonstrate lower HRV measures compared to premenopausal women, though these differences appear due to age and BMI; (2) postmenopausal women demonstrated a decrease in cardioprotective HF HRV in response to a stressor, while premenopausal women maintained this measure of cardiac autonomic tone in response to AngII; (3) in premenopausal women, baseline HRV measures did not differ between the high and low estradiol phases of the menstrual cycle. The gene discussed is AGT; the disease is hydrops fetalis.