Homocysteine (cont.)

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What is considered a high level for homocysteine?

Homocysteine levels are measured in the blood by taking a blood sample. Normal levels are in the range between 5 to 15 micromoles (measurement unit of small amount of a molecule) per liter. Elevated levels are classified as follows:

  • 15-30 micromoles per liter as moderate

  • 30-100 micromoles per liter as intermediate

  • Greater than 100 micromoles per liter as severe

What causes elevated homocysteine levels?

Homocysteine is chemically transformed into methionine and cysteine (similar amino acids) with the help of folic acid, vitamin B12, and vitamin B6. This transformation utilizes a set of mediator molecules (called enzymes) and happens via a delicate sequence of specific steps.

Therefore, insufficient amounts of these vitamins in the body can hamper the natural breakdown of homocysteine. In addition, if there are any deficiencies in the mediator molecules, the breakdown is also hampered. This can cause homocysteine to accumulate in the blood because its breakdown is slow and inadequate.

Can elevated homocysteine levels be genetic?

Homocysteine levels in the blood may be elevated for many reasons as briefly described in the above section. More specifically, these can be divided into severe genetic causes and other milder causes.

In the genetic condition called homocystinuria, there is a deficiency or lack of an important mediator molecule (enzymes) in the complicated homocysteine breakdown pathway. This leads to severely elevated levels of homocysteine. In this rare and serious condition, there is a constellation of symptoms that include developmental delay, osteoporosis (thin bones), visual abnormalities, formation of blood clots, and advanced atherosclerosis (narrowing and hardening of blood vessels). This condition is mainly recognized in childhood.

Milder genetic variations are more common causes of elevated homocysteine levels (hyperhomocysteinemia). In these conditions, the mediator molecules malfunction and are less efficient because of minor abnormality in their structure. They also lead to elevation of homocysteine levels, although much milder than in homocystinuria, by slowing down the breakdown of homocysteine.


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