BH4 - Tetrahydrobiopterin
BH4 is an enzyme that is used to make serotonin, dopamine, thyroid hormones, melanin and to detox ammonia. It is recharged by folate and/or niacin and/or vitamin C.
With certain combinations of the MTHFR gene, some people have a
limited supply of BH4. Those people can probably be identified as those
who have tendencies towards depression, low energy, all-or-nothing
focus, hypothyroid (even subclinical), are pale, and may have elevated
blood ammonia. These people will do best on small amounts of very high quality protein, and lots of methyl folate.
Tetrabiopterin seems to be a common misspelling, and is generating a
bunch of google hits, so I'll include that here, too for those of us who
can't keep *that* many syllables in our heads at once. ;)
Reasons to Suspect
If you have low dopamine AND low serotonin AND low thyroid function (even subclinical). If you have high blood ammonia. If you have MTHFR polymorphisms.
The main way to increase BH4 is by recycling it with folate, niacin and/or vitamin C.
New BH4 can be made from the purine GTP, so high purine foods may be helpful.
Also, the body makes ammonia
when it processes protein, and the BH4 pool is depleted when it detoxes
that ammonia. Limiting dietary protein to the RDA is the most
effective way to keep ammonia levels reasonable.