It could also result from the synthesis of a cystathionase that is so greatly mutated it cannot function at all. On the other hand, vitamin B6 – responsive form still has synthesis of cystathionase. However, the cystathionase has an altered ability to bind to vitamin B6, its coenzyme. This changed interaction lowers the efficiency of cystathionase, so it cannot convert cystathionine as well. Genetics
Cystathioninuria is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.Interestingly, homozygotes and heterozygotes were able to be distinguished in one study through both plasma and urinary levels of cystathionine. The homozygote individuals had cystathionine levels greater than 0.5 moles per milligram of creatinine. Each of the homozygote individuals had a significant amount of cystathionine in the plasma as well. In contrast, the heterozygote individuals excreted approximately one tenth the amount of cystathionine as the homozygote individuals. The heterozygote individuals also had no detectable amounts of cystathionine in their plasma.The gene for cystathionase, CTH, has been sequenced and multiple mutations have been shown to be associated with the development of cystathioninuria. Two nonsense mutations were found in exon 8 and exon 11 of CTH.
Medical uses
Iron supplements are used to treat iron deficiency and iron-deficiency anemia; parenteral irons can also be used to treat functional iron deficiency, where requirements for iron are greater than the bodys ability to supply iron such as in inflammatory states. The main criterion is that other causes of anemia have also been investigated, such as vitamin B12 or folate deficiency, drug induced or due to other poisons such as lead, as often the anemia has more than one underlying cause. Iron deficiency anemia is classically a microcytic, hypochromic anemia. Generally, in the UK oral preparations are trialled before using parenteral delivery, unless there is the requirement for a rapid response, previous intolerance to oral iron or likely failure to respond. Intravenous iron may decrease the need for blood transfusions however it increases the risk of infections when compared to oral iron. A 2015 Cochrane Collaboration review found that daily oral supplementation of iron during pregnancy reduces the risk of maternal anemia and that effects on infant and on other maternal outcomes are not clear. Another review found tentative evidence that intermittent iron supplements by mouth for mothers and babies is similar to daily supplementation with fewer side effects. Supplements by mouth should be taken on an empty stomach, optionally with a small amount of food to reduce discomfort. Athletes
Athletes may be at elevated risk of iron deficiency and so benefit from supplementation, but the circumstances vary between individuals and dosage should be based on tested ferritin levels, since in some cases supplementation may be harmful.