Another paper on BH4 and arterial health was presented at the 2005 American Heart Association’s Second International Conference on Women, Heart Disease and Stroke.  Drs. Richard White and Scott A. Barman, both pharmacologists, found that estrogen targets nitric oxide synthase 1, one of three versions of the enzyme that makes the vasodilator, nitric oxide.  This explains estrogen’s ability to dilate blood vessels and open up blood flow in healthy people. However, they also found that if the creation of nitric oxide is blocked, estrogen constricts blood vessels. Older people are more likely to be deficient in BH4 (tetrahydrobiopterin) and L-arginine, which are needed for the formation of nitric oxide in the lining of blood vessels.

I suspect that this is one reason older women are more likely to experience a loss of circulation to the heart, brain and other organs when they are placed on estrogen. Unfortunately, it isn’t just older women who are in danger when placed on estrogen.  Estrogen depletes folic acid. Folic acid is required to create BH4. Thus all people exposed to excessive estrogen are in danger of compromised circulation.