What is a BH4 loading test?

What is a BH4 loading test?

The most used method is the BH4 loading test. Historically this test was performed at neonatal age, immediately after neonatal screening and aimed to distinguish hyperphenylalaninemic patients with PAH deficiency and patients with a BH4 deficiency [10, 11].

What is BH4 deficiency?

Tetrahydrobiopterin (BH4) deficiency causes the body to build up an abnormally high level of phenylalanine, one of the building blocks of proteins. In addition, BH4 deficiency leads to low levels of certain neurotransmitters, chemical messengers that control many body functions.

How is BH4 deficiency treated?

Treatment of BH4 deficiencies consists of BH4 supplementation (2-20 mg/kg per day) or diet to control blood phenylalanine concentration and replacement therapy with neurotransmitters precausers (L-dopa/CarbiDOPA and 5-hydroxytryptophan), and supplements of folinic acid in DHPR deficiency.

What is tbh condition?

Tetrahydrobiopterin deficiency (THBD, BH4D) is a rare metabolic disorder that increases the blood levels of phenylalanine. Phenylalanine is an amino acid obtained normally through the diet, but can be harmful if excess levels build up, causing intellectual disability and other serious health problems.

How can I increase my BH4 level?

Folate enhances the binding of BH4 to NOS through a pteridine-binding domain and then 5-methyltetrahydrofolate facilitates the electron transfer by BH4 from the NOS reductase domain to the heme. Therefore, folic acid (FA) enhances the chemical synthesis and stabilization of BH4 (2).

What is BH4 used for?

Tetrahydrobiopterin (BH4) is essential for the biosynthesis of dopamine, noradrenaline, and serotonin, which serve as cofactors for tyrosine hydroxylase (TH) and tryptophan hydroxylase. GTP cyclohydrolase (GCH) is the first and rate-limiting enzyme for BH4 biosynthesis.

Is BH4 a vitamin?

Tetrahydrobiopterin (BH4, sometimes THB) is a vital cofactor for numerous enzymes in the body, including those involved in the formation of nitric oxide (NO), and the key neurotransmitters dopamine, serotonin and epinephrine.

How do I get BH4?

BH4 deficiency is acquired in an autosomal recessive manner, which means the disease will manifest when both the copies of the gene obtained from parents have mutations. Both the parents may carry one copy of mutated genes (carriers), although they do not show any signs or symptoms.

What is the name of BH4?

Borohydride is a boron hydride. A class of inorganic or organic compounds that contain the borohydride (BH4-) anion.

What is BH4 made from?

BH4 is made from the molecule GTP (guanosine triphosphate). GTP is converted into BH4 in three stages, which are catalysed (in order) by the enzymes GTPCH, PTPS and SR. These enzymes are coded for, respectively, by the GCH1, PTS and SR genes. Interestingly, rare mutations in these genes can lead to deficiency of BH4.