How does chastity shrink your penis?

I started my chastity journey a few months ago and now my girlfriend locked me up four days ago and said it might be permanent.

I was always very interested in the shrinking effect chastity is said to have. Now my question is: Does being in chastity for a long time really shrink your penis, and if so, how?

If someone could give me a scientific answer that explains how certain aspects of the penis’ anatomy get changed, I’d be super thankful.

Thanks in advance, your cucky whiteboi! xx