<prompt> Answer this question truthfullyWhat does Tetrahydrobiopterin deficiency mean?  <response>: <reason> Treatment of BH4 deficiencies consists of BH4 supplementation 2-20 mgkg per day or diet to control blood phenylalanine concentration and replacement therapy with neurotransmitters precursors L-dopaCarbiDOPA and 5-hydroxytryptophan and supplements of folinic acid in DHPR deficiency. 