Generality
Albumin is the most abundant protein present in plasma.
It is produced by the liver and has three main functions:
- Transport and eliminate waste substances that are expelled with urine (such as bilirubin, fatty acids and hormones);
- Keep the oncotic pressure in balance, which regulates water exchanges between the capillaries and the interstitial fluid that surrounds the blood vessels and wets the tissues;
- Build a reserve of amino acids for the body.
Curiosity
Albumin owes its name to egg white, from which the protein was first isolated.
The dosage of this protein can be performed on a blood sample ( albuminemia ) or urine ( albuminuria ). The test provides useful information on liver and kidney function . Furthermore, the concentration of albumin in the blood reflects the nutritional status of the person .
High albumin values are quite rare, while its decrease can be caused by several factors, which may be transient or result from a real pathology.
Being synthesized by the liver, the concentration of plasma albumin decreases in severe hepatic insufficiencies. Obviously, even serious nutritional deficiencies may explain a generalized decrease in circulating proteins, including albumin. A decrease in plasma albumin can be caused by insufficient hepatic synthesis (cirrhosis), protein malnutrition (Kwashiorkor) or excessive elimination with urine due to alterations of the glomerular filter.
High albumin values are found mainly in dehydration situations.
What's this
For quantity and function, albumin is considered one of the most important proteins in the body. It is synthesized by the liver and is contained above all in interstitial fluids and in plasma, where it represents, by itself, about half of the circulating proteins (55-65% of the total protidemia).
A single gram of albumin can recall eighteen grams of water in the circulatory stream; for this reason it is a fundamental substance for maintaining the normal plasma oncotic pressure.
If too much albumin circulates in the blood, its volume increases excessively, overloading the entire cardiovascular system. Conversely, when plasma albumin concentrations are lowered, water diffuses into the interstitial space (present between one cell and another).
Children suffering from severe malnutrition have a particularly swollen abdomen precisely because of the reduced concentration of albumin in the plasma (hypo-albunemia). When subjected to important caloric and protein deficiencies, the body defends itself by catabolizing its proteins; consequently the protein and plasma protein concentration decreases. If there are few proteins in the blood, and therefore few albumins, the oncotic pressure decreases and the water passes from the blood to the interstitial spaces, where it accumulates conspicuously causing the characteristic "big belly".
In addition to regulating oncotic pressure, albumin acts as a "non-specific carrier"; this protein is in fact able to bind to itself and convey many substances in the plasma, such as free fatty acids, steroid hormones, bilirubin, some drugs and certain vitamins.
Under conditions of necessity albumin can also be used by tissues as a source of amino acids to cover the nutritional needs of the cells.
Albumin turnover is high: 50% of the molecules produced are degraded within 10 days.
Why do you measure
The concentration of albumin in the blood is an indicator of the subject's nutritional status (particularly in hospitalized patients) and of renal or hepatic function.
Furthermore, this parameter can be indicative of various disorders and pathologies.
When is the exam prescribed?
Albumin is normally included in control examination panels, so it is frequently used in assessing a person's health status.
The doctor may prescribe the test in the presence of some symptoms:
- Weight loss for no apparent reason;
- Fatigue;
- Jaundice (yellowish color of the skin);
- Edemas (swellings);
- Swelling around the eyes, stomach or legs (symptoms of nephrotic syndrome).
Clinical indications of albumin dosage
The albumin test can be indicated for:
- Evaluate liver function, as part of the liver panel;
- Assess renal function, along with creatinine and blood urea (BUN);
- Diagnostic framework of the edema;
- Monitor changes in health status resulting from treatment or disease progression.
The doctor can also prescribe the measurement of albumin to ascertain the nutritional status of a person (for example, if there has been a significant weight loss).
Normal values
The plasma albumin levels are normally between 3.5 and 5.5 grams per 100 milliliters (35-55 g / Liter).
High Albumin - Causes
HYPERALBUMINEMIA: Abnormal concentration of albumin in the blood.
An increase in the protein at the plasma level is frequent during the morbid states that subtract water from the body, with consequent appearance of dehydration :
- Persistent vomiting and diarrhea;
- Extensive burns;
- Addison disease;
- Diabetic coma.
High albumin values in the blood may also depend on:
- Sarcoidosis (systemic inflammatory disease);
- Buerger's disease or tromboangioite obliterans (a disease affecting blood vessels and arteries).
Low Albumin - Causes
HYPOALBUMINEMIA: decrease in plasma albumin levels below physiological values.
A reduction in albumin in the blood can be caused by all those conditions in which they exist:
- Protein deficiency due to reduced dietary intake (Kwashiorkor);
- Bad absorption (enteropathies, celiac disease, Crohn's disease, protein intolerances);
- Increased catabolism (severe inflammation, febrile states, cachexia, neoplasias, hyperthyroidism, hypercortisolism or Cushing's syndrome, overtraining);
The plasma levels of albumin also decrease following pathologies that affect the liver (the ability to synthesize fails) and the kidney (increase elimination).
The concentration can decrease, in particular, when they are established:
- Liver cirrhosis (is the most common cause);
- Acute and chronic hepatitis;
- Genetic anomalies (synthesis of defective albumins);
- Nephrotic syndrome and glomerulonephritis.
The hypoalbuminemia that is observed in pregnancy is attributable both to hormonal modifications (which alter the vascular permeability and the functionality of numerous organs), and to the increased utilization of proteins by the fetus.
How to measure it
The albumin test is part of routine blood tests. This is done by simply drawing from the vein of an arm.
Factors influencing the exam
- Patients taking large amounts of intravenous fluids may experience dilutional hypoalbuminemia.
- The presence of hyperlipidemia (many fats in the blood) can alter the outcome of the examination.
- Pregnancy and oral contraceptives can also decrease albumin levels.
- Some drugs cause an increase in blood albumin, such as anabolic steroids, androgens, growth hormones and insulin.
- Albumin variations are also found in vegetarian diets and hemolysed samples.
Albumin in Urine
The presence of albumin in the urine is identified by the medical term ALBUMINURIA and there is a specific test, called microalbuminuria, capable of detecting its concentration even when it is present in extremely limited quantities.
High levels of albuminuria are indicative of poor kidney function (typical of late-stage diabetes), while minor amounts can be linked simply to the excesses of a high-protein diet, a particularly heavy physical activity or the same pregnancy.
Preparation
For blood sampling, you must be fasting for 8-10 hours .
Moreover, before undergoing the examination, it is necessary to avoid carrying out intense physical efforts, since this can interfere with the values of the albumin.
Interpretation of Results
- High Albumin - An increase in albumin in the blood may be due to dehydration secondary to vomiting or dysentery. These conditions cause a decrease in the liquid part of the blood.
- Low Albumin - A reduction in albumin in the blood is a warning signal and represents an indication for the continuation of clinical investigations. The reduced value of the protein may be indicative of a transient condition that can be resolved without particular treatments or it can suggest the presence of acute or chronic pathologies that need timely medical interventions.
A low level of albumin may depend on serious nutritional deficiencies (poor protein intake or malnutrition) and malabsorption (Crohn's disease, celiac disease or conditions in which there is a great loss of protein in the intestine). Being synthesized by the liver, the concentration of plasma albumin also decreases in severe liver insufficiencies.
A drop in albumin can be caused by excessive elimination with the urine due to alterations of the glomerular filter of the kidneys. In the latter case it is possible to measure the amount of albumin or protein in the urine (urinary albumin).
