VERIFIED CONTENTAuthor: lek. Mariusz Basiura

Albumin (from the Latin word albus meaning literally white or light) belong to proteins, high-molecular polymers made of amino acids, which are the basic component of both animal and plant organisms. In the human body, albumin is mainly found in the blood plasma and extravascular space, and is produced in the liver.

What areAlbumin ? In order to learn about the role ofalbuminin our body, we should learn, at least to a small extent, about the chemical structure of these proteins. Albumin belongs to the group of globular proteins, this group also includes globin (the same that is part of hemoglobin), histones - proteins that bind to DNA, protamine, antibody-building globulins and prolamine.

Contrary to fibrillar (filamentous) proteins, albumin has a spherical shape and is soluble in water and in aqueous solutions of bases and acids (hydrophilic). Thanks to this, they can carry various types of water-insoluble compounds that, attached to albumin, move with the blood throughout the body.

Another special feature of albumin is amphiproticity. As ampholytes, or amphoteric electrolytes, albumin contains both acidic and basic residues. This feature allows them to bind both anions and cations.

It is another, apart from hydrophilicity, feature that favors the binding of various substances and their transport in the body. In addition, this structure is important in fulfilling one more function of albumin - the so-called a protein buffer to help maintain a constant blood pH.

Albumin - features

Maintaining a constant oncotic pressure

One of the main roles of albumin in the human body is maintaining constant oncotic pressure - that is, regulating the amount of water in the blood and preventing it from leaking from the plasma into the tissue fluid. This function results from the protein concentration in the plasma, which is significantly (about 3-4 times) higher compared to the concentration in the intercellular fluid.

The oncotic pressure somewhat balances the hydrostatic pressure of the blood and thus prevents the passage of water with electrolytes outside the vessels. In other words, it reduces the likelihood of swelling. Albumin is the main one in this caserole, as they constitute as much as 60% of all plasma proteins.

Transport function

Albumin transports a huge amount of various small molecules, starting with certain hormones (thyroxin, triiodothyronine, cortisol), drugs (including antibiotics, barbiturates), fatty acids, lipids and bile pigments (bilirubin), vitamins. Albumin also plays a role in the transport of e.g. nitric oxide.

Compared to other proteins (haptoglobin, transferrin) they are nonspecific but key transporters. In addition, various metal cations such as calcium (Ca), sodium (Na), magnesium (Mg), zinc (Zn), and potassium (K) can also bind to albumin and move in this form around the body.

Hence, in the results of laboratory tests of our blood, there is sometimes a distinction between ionized and total calcium. This allows for the summary determination of the concentration of this protein (including the part associated with proteins and in the form of a free cation).

Blood pH maintenance function, buffer

As mentioned before, due to their amphiprotic chemical structure, albumin is part of the blood buffer system. The protein buffer (the main component of which is albumin), apart from the carbonate and phosphate buffers, is responsible for maintaining a constant pH of the blood, amounting to about 7.35-7.45.

Disturbances in this balance can lead to acidosis (acidification of the body) or alkalosis. The constant pH of the blood of our body is extremely important for the biochemical changes taking place in it. Its constant value is one of the basic conditions for all physiological processes in the body, from respiration and digestion of food to the excretion of harmful metabolites.

Chemical reactions together with enzymes catalyzing them require appropriate temperature and pH for proper operation.

Albumin - antioxidant, free radical scavenger

Interestingly, human albumin, due to the fact that it is the main extracellular source of reduced sulfhydryl groups located in cysteine, enables the capture of free radicals. By binding ions of metals such as copper, cob alt, nickel, zinc and iron, which inhibit the formation of free radicals, it represents one of the main antioxidants in our body. So it is a kind of guardian that protects us against these harmful products of chemical changes taking place in our body.

Serum albumin - norms

The correct level of albuminin the serum of the human body should be within 35-50 mg / ml of blood. Remember, however, that the values ​​of laboratory testsalways refer to the standards given by the designating unit. They depend both on the patient's sex, age and the method of determination. We always present the obtained result to our doctor.

Causes of hypoalbuminemia

At the outset, it should be noted thatlowering the albumin concentration(hypoalbuminemia) is a phenomenon much more frequent than its increased value (hyperalbuminemia).

Hypoalbuminemia- i.e. lowering the albumin value below the lower limit of the norm. It may be related to the decreased production of these proteins by hepatocytes as well as indicate their loss by the body.

Liver failure may have a different etiology, lead to fatty liver disease, and the decrease in albumin is one of the basic parameters that allow the assessment of liver function. The liver is where these proteins are produced. Albumin (along with other proteins marked in the proteinogram) is part of the so-called hepatic profile, i.e. a set of tests allowing to partially assess its condition.

In addition, they are marked with, among others such parameters as:

  • total bilirubin
  • Aspat
  • Alat
  • GGTP
  • ALP
  • LDH
  • proteinogram
  • testing for viral hepatitis

Nephrotic syndrome . When our kidneys are sick and blood filtration does not take place properly, the body loses various components with urine, including proteins. When the loss of protein in the urine exceeds 3.5 g per day, and in addition, there are specific symptoms, we can diagnose nephrotic syndrome.

It is worth adding that the process of protein excretion in the urine (albuminuria) is to some extent a physiological phenomenon. When protein loss is too high, evaluation for glomerular damage should be made. The most common causes of glomerular damage include: diabetes mellitus, arterial hypertension, and glomerulopathies.

Inflammation- albumin belongs to the group of so-called negative acute phase proteins, its concentration decreases in inflammation. In the margin. A protein belonging to the positive acute phase proteins is, for example, often marked CRP (C Reactive Protein).

Hyperhydration- when our body begins to accumulate excessive amounts of water, for example due to impaired kidney function or in the syndrome of inappropriate ADH secretion (SIADH), the level of albumin drops below normal.

Diseases of the gastrointestinal tractsuch as Crohn's disease, celiac disease or PLE. PLE-protein losing enteropathy is a disease in which protein is also lost. This pathology is associated withinflammation of the intestinal mucosa and with disturbances in the structure and function of their lymph vessels.

Malnutrition- the level of albumin also allows you to monitor the he alth condition - especially the level of nutrition of the body, in the case of malnutrition (resulting from various reasons: lack of food, cancer and anorexia ). In these cases, the level of albumin (prealbumin, transthyretin) is significantly lowered. So it is an important test to find the cause of your sudden weight loss.

Pregnancy- it is also a moment of rapid changes in the woman's body, and the reduction in the amount of albumin may result, among others, from from the physiological increase in the volume of blood circulating in the mother's body.

Neoplastic process- in neoplastic diseases we can also find a decreased level of albumin. However, it should be remembered that this is a single study and we cannot draw too many conclusions on its basis.

A much rarer situation is the detection of an elevated level of serum albumin, when the main cause is dehydration.

Low albumin - symptoms

Symptoms related to hypoalbuminemia are very nonspecific and we can mention here, among others :

  • weakness
  • feeling unwell
  • nausea and vomiting
  • chronic diarrhea
  • ascites
  • swelling around ankles, but also swollen eyes
  • malnutrition and in extreme cases even cachexia

Albumin - study

Serum albumin determinations are made from blood drawn from a fasting patient. The last meal should be consumed by 6 p.m. on the day preceding the examination.

Low Albumin Treatment

A disturbance in albumin values ​​alone can never be a reason to start treatment. The results of all determined laboratory parameters must be analyzed, and most of all, the clinical condition of the patient. In case of any doubts, consult a doctor who may decide to perform further tests and implement possible treatment.

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