Tetrahydrobiopterin (BH4) deficiencies are a heterogeneous group of disorders caused by a defect in two of the three enzymes involved in its biosynthesis or in the two recycling enzymes. Except for the deficiency of dehydratase. an enzyme catalyzing a reaction in the recycling pathway. all other variants of BH4 deficiency are characterized by developmental delay. https://parisnaturalfoodes.shop/product-category/keratin-cond/