I’ve discussed my views on this before I’ve pasted part of the thread below.
In short - a stiffness index can be defined as the ratio of diastolic and systolic blood pressure divided by the change in artery diameter examined by ultrasound.
Stiffness index = pressure ratio/change in diameter
Study: Estradiol Inhibits Penile Erection, Particularly at the Penile Base
This is a long one stick with me…
I see two mechanisms for the e2 and ED relationship.
- High e2 affecting the brain and not signalling adequate NO production.
- High e2 affecting the dick veins that carry the blood to an erection and the veins that allows the blood to exit the erection.
To address point 2 only- it’s been proven in the papers listed above that higher e2 is correlated with reduced arterial wall stiffness. This means that for a given pressure, a less stiff arterial wall will distend more than a stiffer one.
To define stiffness in terms of materials science where in this case the material is human tissue which exhibits viscoelastic characteristics(stretches under tension over time)- stiffness is defined as the ability of a material to resist deformation when subjected to a given force.
To describe an erection in some physical sense. There is an inlet, volume chamber and an outlet.
Blood flows in through the inlet, the larger the diameter of the inlet the easier the blood will flow. This is good for erection obviously and is the essence of PDE5 inhibitors.
The pressure in the chamber I.e the penis, will increase and expand until final volume is reached only if the rate of flow at the inlet is greater than the rate of flow at the outlet.
I would like to focus on the rate of flow at the outlet.
If oestrogen can change the material strength of the exit vein tissue, might it become too weak too control the flow out of the penis? If so, this could easily lead to an increased outlet flow rate and an inversely proportional decrease in erection pressure inside the chamber.
I am attempting to present food for thought and merely a hypothesis as to why some people do well with higher e2 numbers and some don’t. Giving the above, it’s quite clear that our veins and arteries will all have different material properties namely stiffness. A primary cause of ED in older guys is a plaque build up in arteries which makes them stiffer. It might simply be a case of TRT and an increase e2 helps guys achieve erection if they have stiffer arteries to begin with. This also ties in with properly managed TRT that yields adequate e2 levels is a good thing for the cardiovascular system as a whole as stiff arteries is not good. Pulse pressure can be an indicator of arterial stiffness.
Younger guys for example or anyone who’s arteries are below a certain stiffness might have issues. The increase in e2 might make their outlet vein too ductile and unable restrict flow to adequately maintain and erection.
Like I said just a hypothesis, you can find papers on everything I’ve discussed individually but I’ve not seen anything investigating the bio mechanical relationship with e2 and dorsal vein stiffness directly.
If you think the hypothesis is utter nonsense please do let me know….
PubMed
PP is an easy method to estimate and quantify patient arterial stiffness. We demonstrated here for the first time that elevated PP is associated with arteriogenic ED and male hypogonadism. The calculation of PP should became more and more familiar in…
PubMed
The investigation presented in this study reveals the effect of each material parameter on the viscoelastic arterial response. Thus, a better understanding of the behavior of viscoelastic arteries is achieved.