GTP-CH Deficiency

GTP-CH Deficiency General Information

GTP cyclohydrolase (commonly abbreviated as GTP-CH) is an important enzyme that plays a capital role in the biosynthesis process of biopterin and / or folate. Furthermore, this enzyme is also responsible for the hydrolysis of guanosine triphosphate (commonly abbreviated as GTP), transforming it into 7,8-dihydroneopterin 3'-triphosphate.

Guanosine Triphosphate Cyclohydrolase Deficiency (widely abbreviated as GTP-CH Deficiency) is a very rare metabolic medical condition that leads to the lack of the important BH4 (tetrahydrobiopterin) cofactor which is known to play an important part in turning phenylalanine (an amino acid) into tyrosine (another amino acid) and then into dopamine. Another responsibility of this cofactor is the transformation of tryptophan into serotonin. The presence of GTP-CH is capital in the maintaining of a regular production of dopamine and serotonin. Without this important cofactor, the body experiences a deficiency of neurotransmitters (both in the central and peripheral nervous system).

We currently know two forms of this medical condition (GTP-CH Deficiency). The first and the most commonly encountered is Segawa Disease (the autosomal dominant form of this disorder). Patients who have been diagnosed with this medical condition respond quite well to the dopamine replacement treatment. The second form of this disorder is not as commonly encountered; this is a recessive form and it does not provide an effective response to most therapy options. The presence of these deficiencies easily leads to the development of movement disorders, neurological impairment, autonomic symptoms (temperature irregularities, blood pressure instability, and so on). This type of disease is more common in female patients than in male patients.

GTP-CH Deficiency Symptoms

Like most other medical conditions, the presence of the GTP-CH Deficiency (GTP cyclohydrolase deficiency) leads to the development of several unusual and / or disturbing symptoms that enable the physician set a proper diagnosis. After studying several patients who have been diagnosed with this medical disorder, scientists have completed a list of the most common signs and / or symptoms that this medical condition is known to generally trigger. Thus, most individuals with GTP-CH Deficiency presented an increase in their levels of urine phenyl-ketone, psychomotor retardation, drowsiness, convulsions, irritability, tremors, poor muscle tone in the patient’s trunk (in contrast with the increased muscular tone of the patient’s limbs), increased salivation, hyperthermia, and so on. Other neurological signs included a retarded development, abnormal movements, increased difficulties in performing simple actions (such as swallowing).

It is an easily noticeable fact that these signs and / or symptoms are quite common, as they can be triggered by the presence of other medical conditions, apart from GTP-CH Deficiency. For this reason, in order to set a proper diagnosis, you personal health care provider might want you to undergo a set of clinical exams (medical tests) that will enable him or her to find out the true cause of your symptoms. The disorder’s prognosis is known to be better if the medical condition is discovered and treated in due time. For this reason, we strongly advise all patients to seek professional medical help as soon as they present any unusual and / or disturbing symptoms. Furthermore, as some medical conditions are known to remain hidden (without triggering any symptoms) until their latest (most severe) stages, it is very important for all individuals to undergo regular clinical check-ups.

GTP-CH Deficiency Treatment

The settling of a proper diagnosis of this medical condition is known to be based upon a three stage clinical testing procedure. The first stage involves a spinal tap (a lumbar puncture) that is able to determine the presence of any abnormalities of the organism’s neurotransmitter metabolites. This is not a routine clinical procedure and it should be performed only by a specialist who has experience in this area. The results of this stage of testing will show whether the patient will have to perform the stage 2 and / or 3 of the diagnosis procedures. In the second stage of the procedures, the patient who is suspected to suffer from GTP-CH Deficiency has to ingest a large amount of phenylalanine. After this, his or her blood will have to be drawn and carefully analyzed at pre-set time intervals. This clinical procedure is quite similar to the glucose tolerance medical tests that diabetic patients need to undergo. The results of this exam will show whether the individual presents hyper-phenyl-alaninemia or not. The third (and last) stage of the diagnosing of this disorder (GTP-CH Deficiency) involves the analyzing of the individual’s GTP-CH gene. The results of this clinical exam need a longer period of time to come in.

For now, the most commonly prescribed therapy in the case of patients who are suffering from this medical condition (GTP-CH Deficiency) is the intake of medical products (medicines) that are able to help the individual restore his or her regular dopamine levels. As dopamine itself is unable to directly cross the blood-brain barrier, most physicians recommend the intake of L-Dopa, often accompanied by carbidopa. Some medical products (such as Sinemet) are commercially available drugs that are known to contain both L-dopa and carbidopa. However, a therapy with this drug is not recommended in the case of children, as the available dosages have proven to be too high in carbidopa and L-dopa for them, making their initial symptoms even more severe. The therapy of children who have been diagnosed with GTP-Ch Deficiency is quite problematic, as they are known to be very sensitive to almost all of the drug’s side effects. For this reason, their therapy with L-dopa and carbidopa must be accompanied by the intake of gastrointestinal drugs, serotoninergic medicines, anticholinergic drugs (such as Artane).

All patients who are suffering from this disorder (GTP-CH Deficiency) should try occupational and physical therapy, as such treatment methods may sometimes prove to be very effective. Children have a lot to benefit from speech therapy. Some scientists sustain that research in stem cell transplants and / or gene therapy might give the answer to cure this medical condition. All patients who are suffering from this medical disorder should know that there are various anonymous support groups world-wide who are able to offer help and support to those in need.