Found this fascinating... "Resting sympathetic outflow is greater during the luteal phase – when both oestrogens and progesterone are elevated – compared with the early follicular phase of the menstrual cycle – when both oestrogens and progesterone are low (Minson et al. 2000a; Carter et al. 2009b; Fu et al. 2009). During an orthostatic challenge, total MSNA (which takes into account the area under the MSNA burst) is also greater in the mid-luteal versus early follicular phase (Carter et al. 2009b; Fu et al. 2009) (Fig. 2)." In other words, the sympathetic (fight or flight) response that causes tachycardia, tunnel vision, digestive issues, nausea, and so on (a.k.a. dysautonomia), is increased in relation to the amount of reproductive hormones in the system. Makes sense, considering a majority of POTs patients are women between 15 and 50. This was taken from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3530109/ Nina Stachenfeld's research is focused on how hormones impact orthostatic tolerance. Very insightful stuff for those who believe they have POTs due to hormonal imbalances. I hope the POTs doctors are paying attention to her work. The good news is that estrogen, a potent vasodilator, drops after menopause. For women with chronic low blood pressure (a common trigger for adrenaline release) that could mean more normalized blood pressure and hopefully fewer instances of tachycardia.