When estrogen gets too low, the brain realizes estrogen is no longer high enough to protect the body and do its job, so the adrenal gland kicks in and increases cortisol secretion to excess.
This excess is enough to cause an instability of the blood pressure, appearing as a vacillating hypertension, both systolic and diastolic.
The diastolic pressure becomes less increased than the systolic, resulting in a larger pulse pressure, then resulting in a visceral response creating a hot flash.
Hot flashes are present only when estrogen falls too low and will go away once estrogen has been fully restored.
Estrogen is responsible for regulating everything in the female body including blood pressure and body temperature.
Hot flashes are one of the clinical indicators of estrogen deficiency we measure in the hormone clinic. As long as estrogen remains in optimal blood serum ranges, hot flashes do not exist. The absence of hot flashes is one of the ways we know hormones are balanced.
If you are on hormone therapy and you are getting hot flashes, then your hormones are not properly balanced.
If you want to know where you stand with your own hormone balance, I encourage you to take the Hormone Balance Test. It will give you a good place to start on your journey to getting your hormones balanced to your Hormone Sweet Spot™.
Freedman RR. Physiology of hot flashes. Am J Hum Biol. 2001 Jul-Aug;13(4):453-64.