Albumin is the most abundant protein in human blood. It makes up 60% of the proteins in the blood. It is found in other tissues besides blood vessels. In fact, about 30-40% of the total albumin in the body is found in the blood vessels. It contributes to maintain a certain level of blood pressure in blood vessels. Albumin is also a good carrier of metabolites, molecules, and substances that need to be transported, such as drugs, in the blood. Albumin also has a very important function in maintaining blood pH.
In a normal person, the albumin level in the blood is about 40 g/L. Serum albumin levels in newborns are lower than in adults. Albumin is produced only in liver cells. However, it is not stored in the liver. In a normal adult, the liver can produce an average of 14-15 g/L of albumin per day. In fact, the liver can increase this production rate up to 3-4 times if needed. Therefore, in diseases that cause damage to liver cells, albumin levels in the blood decrease and can cause life-threatening problems.
If the amount of albumin is in excess, it is broken down in the endothelial cells on the inner surfaces of the vessels. Albumin is broken down most in muscle and skin tissue (50%). In addition, 15% is broken down in the liver and 10% from the gastrointestinal tract. The loss of albumin by the urinary system is very small.
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The main substances known to carry albumin in the blood are:
- Fatty acids (oleic, linoleic, linolenic, aracidonic, palmitic and myristic acids, etc.)
- free radicals
- Some toxic metabolic products
- Metals that can be toxic in high amounts (zinc, copper, cadmium, mercury, gold, silver and nickel etc.)
- nitric oxide
- thyroid hormones
- Steroids
- bilirubin
- Most drugs
- Vitamin B6
- vitamin A
- Calcium
- Magnesium
- Uremic toxins
- thiol-containing endogenous compounds such as L-cysteine and homocysteine
- bacteria
- Noble gases (xenon, krypton and argon, neon and helium etc.)
- Some antioxidants, such as resveratrol
The factors that affect the synthesis of albumin in our body can be briefly listed as various factors including nutritional status, serum oncotic pressure, cytokines and hormones. Inhibitory substances associated with inflammatory conditions, such as TNF and IL-1, may also affect albumin synthesis and functions.
In albumin tests, the low level of albumin in the blood is more important and can cause many problems in the body.
The most common causes of low blood albumin levels (hypoalbuminemia) are:
- Inflammatory events
- Nutritional disorders in which protein intake is reduced
- Cases of decreased albumin production
- Protein energy malnutrition
- Liver failure
- Primary synthesis defects
- acidosis
- acute phase reactions
- some cytokines
- some hormones
- Situations in which albumin fragmentation is increased
- Protein-losing enteropathies
- burns
- Nephrotic syndrome
- Conditions that cause albumin to escape into the tissues in the vessel walls
- sepsis
- hemodilution
- redistribution
The decrease in albumin level in the blood can cause hundreds of different clinical problems because the drugs that need to be transported and many other molecules cannot be transported to the points where they are needed.
The most common causes of an excess of albumin in the blood (hyperalbuminemia):
- dehydration
- HIV AIDS
- Monoclonal gammopathy
- Multiple myeloma
- amyloidosis
- Chronic inflammatory conditions
- bone marrow disorder
High albumin levels in the blood can cause symptoms such as diarrhea, fatigue, dizziness when standing or sitting, unexplained weight loss, fever, tingling or numbness.
When a decrease or increase in albumin level in the blood is detected, other accompanying symptoms or diseases should be evaluated together. In these cases, your doctor may also refer to further tests to evaluate the complications of your diseases.
In some chronic diseases (diabetes, systemic lupus erythematosus, etc.), the disease may cause complications at different levels by using albumin in the blood, independent of the blood albumin level. For example, in diabetic patients, long-term binding of albumin with glucose may cause kidney or eye problems. For these reasons, in some chronic diseases, it is necessary to monitor the blood albumin level in periodic controls and to evaluate the organs separately.
While albumin level affects the mortality of some diseases in many clinical situations, it is also used as a part of treatment.