Estrogen, contrary to popular belief, is a stress hormone. Estrogen is not the primary female hormone, however, it is necessary for the proper functioning of the body for both genders; it is not the primary female hormone.
Progesterone is THE female hormone produced at 1000 times the amount that estrogen produced inside the female body. No that was not a typo. There is 1000 times more progesterone than estrogen when looking at the hormonal status of most healthy women.
Estrogen, when it comes into the scope of the cardiovascular system, leads to vascular permeability, hence why women during the menstruation period bleed in excess and can even experience nose bleeds. Estrogen is also one of the hormones that are responsible for excessive water retention within the cells. This tends to lead to premature cellular division and a whole host of other nasty things.
When excessive estrogen is in the bloodstream we see increased retention of water in the endothelial cell. This swelling of the endothelial cells leads to less diameter in the blood vessel resulting in a smaller area for blood to flow through, increased blood pressure, and more stress on the heart (vascular resistance).
When it comes to the health of the heart there are things that are inotropic (increase the power of contraction of the heart) and things that are lusitropic (things that promote relaxation of the heart). Estrogen has a negative relationship with both of these, meaning that it is a negative inotropic and a negative lusitropic hormone, interfering with optimal functioning of the heart whenever it is in excess in the body.