Albumin: what is it and what are its functions in the human body?
Let's see what albumin is and why this protein is important for our health.
Blood is a liquid connective tissue that circulates in the vessels and capillaries, veins and arteries of all vertebrate animals. Humans have an average of 5 liters of Blood in the body, and our heart pumps about 70 milliliters per heartbeat, that is, almost all the blood present in the whole organism in a single minute.
In addition to the red blood cells that give it its color, blood also carries many other molecules with diverse physiological functions. This is the case of blood or plasma proteins, which are responsible for the transport of lipids, hormones, vitamins, minerals and various immunological actions.
In the following lines we are going to collect the characteristics of the most prevalent and, surely, the most important blood protein. Stay with us, as this time we dissect the secrets of albumin and its medical the secrets behind albumin and its medical implications..
What is albumin?
Albumin is a small, relatively symmetrical protein found in many structures of animal origin: blood, milk, egg white and the seeds of certain plants.. In humans it represents 54.3% of plasma proteins, i.e. it is the most abundant of all proteins (3.5-5 g/dl).
It may sound a bit strange to say that albumin is the most abundant plasma protein, since we are all used to thinking of hemoglobin as the queen of blood proteins, right? It is curious to know that hemoglobin is not considered in this group because it is transported inside red blood cells, not in the plasma. Therefore, however abundant it is inside these cell bodies (450 mg/ml), it is not conceived as a plasma protein per se.
Here is some relevant information to contextualize the importance of albumin in the human body:
- The liver produces 9 to 12 grams per day of this complex substance.
- Approximately 60% of albumin is located in the extravascular space, i.e. outside the blood vessels.
- Because of its strong negative charge, albumin is a water-soluble protein.
- Its life cycle in the blood circulation is 12 to 20 days.
- Its turnover rate is 15 grams per day. Unlike other substances, there are no albumin reserves in any part of the human body.
The most important function of albumin is the regulation of oncotic pressure, necessary for the proper distribution of fluids in and out of tissues.which is necessary for the proper distribution of fluids in and out of the tissues. Let us dwell for a moment on this unique term, as it is of great medical and biological interest.
Albumin and its functions
Oncotic pressure is defined, medically, as the osmotic pressure of a colloidal solution or dispersion. There is little difference between being told this and knowing nothing about it, which is why we offer a slightly friendlier meaning for the general public: it is a type of osmotic pressure caused by the difference in plasma proteins between the blood plasma (inside the blood vessels) and the interstitial fluid (the space between the cells, one sex between the cells). (space between cells, one-sixth of body tissues).
As the blood capillaries are not very permeable to large plasma proteins (such as albumin), these are usually kept inside the plasma instead of being distributed throughout the interstitium. Due to this protein concentration gradient (greater in the blood than in the interstitial fluid), water enters the blood vessels in an attempt to "balance" this difference. In summary, we can say that this event maintains the correct distribution of body fluids in our body and allows their movement.
Even so, maintaining the oncotic pressure simply by its presence in the plasma is not the only function of albumin. Among many others, we can list the following:
- It facilitates the metabolism and detoxification of various substances, such as bilirubin, metals, ions or enzymes.
- It enhances the elimination of free radicals, harmful products generated during cellular respiration.
- It transports thyroid and fat-soluble hormones.
- Transports free fatty acids and unconjugated bilirubin, as well as many other substances.
- It controls pH.
What is the blood albumin test?
As redundant as it may sound, it is necessary to clarify that the blood albumin test measures the amount of albumin in the patient's blood.. It is a measurable quantification of liver function, since it is synthesized in the liver, providing information on its condition and functioning.
On the other hand, a low level of albumin in the blood may also be indicative of kidney function failure, since in these cases this protein is excreted in the urine when it should not be (an event known as albuminuria). A healthy kidney in no case allows albumin to pass from the blood into the urine.
In general, this test is usually recommended for patients who come to the clinic with jaundice or yellowing of the skin (increased bilirubin concentration in the tissues), weight loss, fatigue, dark-colored urine, or pain under the right rib, the site of the liver.
The normal serum albumin concentration is 3.5 to 5 grams per deciliter.. A lower than normal value is known as hypoalbuminemia and may indicate one of the following disorders which we summarize briefly in the following lines.
This condition is the final consequence of a previous pathology in which liver cells have been destroyed, which has caused their replacement by scar tissue, reducing the effectiveness of the organ itself.
The World Health Organization (WHO) estimates that 27,000 people die annually in high-income countries from this condition, which, to no one's surprise, is linked to chronic alcoholism. which, to no one's surprise, is linked to chronic alcoholism. Cirrhosis of the liver is not the only condition generated by alcoholism, as it is estimated that more than 5% of all deaths worldwide are due to alcohol consumption (no more and no less than 3,000,000).
More than 462 million people in the most disadvantaged areas of the world show signs of nutritional insufficiency. Hypoalbuminemia is one of them, as it is caused by a lack of protein intake.
Albumin is synthesized in the liver from amino acids obtained from the metabolism of dietary proteins, which is why low values of albumin in the liver can lead to a lack of protein intake.For this reason, low values of albumin and malnutrition of the patient are clearly linked.
3. Other causes
While malnutrition and cirrhosis of the liver are usually the most common causes of low blood albumin, there are many other conditions that can lead to albumin deficiency.. To close today's topic, here are some of the most relevant ones:
- Some type of renal dysfunction, such as an infection in the kidneys.
- Liver cancer. More than 800,000 people are diagnosed with this condition annually.
- Congestive heart failure or pericarditis.
- Stomach problems, such as lymphomas or Inflammatory Bowel Disease (IBD). This is often accompanied by nausea, vomiting and diarrhea.
- As a side effect of other diseases or the intake of certain drugs.
It should be noted that in patients with hypoalbuminemia, the administration of albumin for medical purposes may be considered.. Its dosage and rate of administration depend on the individual's conditions, which consist of blood pressure, pulse, hemodynamic status, hemoglobin and hematocrit concentrations, plasma protein content (the oncotic pressure described above) and the degree of venous and pulmonary congestion. A total of 125 grams of albumin may be administered every 24 hours.
As we have seen in this space, albumin is the most present protein in plasma. is the protein most present in the blood plasma and performs multiple functionsFrom the transport and metabolism of various substances to the maintenance of oncotic pressure, this molecule is essential for the correct physiological balance of the organism.
Whether due to excessive excretion by the kidneys or deficient synthesis in the liver, a lack of serum albumin can result in swelling of certain body areas, fatigue, muscle weakness and many other clinical signs. Although this condition can be caused by many events, alcoholism and malnutrition are two of the most common. Once again, we see that every particle that makes up our body is essential for the maintenance of our body's physiology and functions.
- Albumin (in blood), Mhealth.
- Albuminuria, NIDDK.
- Hankins, J. (2008). Role of albumin in water balance. Nursing (English Ed.), 26(10), 42-43.
- Hypoalbuminemia, chemocare.com.
- Oncotic pressure, Clínica Universidad de Navarra.
(Updated at Mar 28 / 2023)