Albumin is the most abundant protein found in blood plasma, the liquid portion of blood. It is a water-soluble, globular protein produced by the liver. This protein makes up approximately half of all the proteins present in serum. The liver’s production rate of albumin is influenced by a person’s protein intake.
Maintaining Fluid Balance in the Bloodstream
A primary function of albumin is regulating fluid distribution between the blood vessels and the body’s tissues. It achieves this by maintaining what is known as colloid osmotic pressure, or oncotic pressure. This pressure is the force that draws and holds water within the circulatory system. Albumin acts like a sponge, ensuring that the fluid component of blood remains inside the vessels rather than leaking out into the surrounding tissues.
This mechanism is directly related to the concentration of albumin in the plasma. When levels are adequate, the osmotic pressure is stable, and fluid is properly retained. A significant drop in albumin concentration weakens this pressure, allowing fluid to escape from the capillaries and accumulate in the interstitial spaces between cells.
This leakage of fluid into tissues manifests as edema, which is swelling commonly observed in the legs, ankles, and feet. In more severe cases, fluid can accumulate in the abdominal cavity, a condition known as ascites.
Transporting Substances Throughout the Body
Albumin functions as the primary transport vehicle for many substances that are not easily soluble in water. By binding to these molecules, albumin allows them to be carried efficiently through the bloodstream to various parts of the body.
Among the substances it transports are several types of hormones, including thyroid hormones and steroids. It also binds to and carries fatty acids, which are used for energy, and bilirubin, a waste product from the breakdown of red blood cells, to the liver for processing. Minerals like calcium are also transported by albumin, and changes in albumin levels can affect the amount of free, active calcium in the blood.
This protein plays a part in pharmacology by binding to various medications. This binding affects how drugs are distributed throughout the body, their availability to target cells, and the speed at which they are metabolized and cleared. The efficacy and required dosage of certain drugs can be influenced by a person’s albumin levels, as lower levels may lead to a higher concentration of the free, active form of a drug.
Causes of Abnormal Albumin Levels
Deviations from the normal range of albumin can indicate underlying health issues. Low albumin, or hypoalbuminemia, is the more common condition and can stem from several distinct causes. Severe liver disease, such as cirrhosis, impairs the liver’s ability to synthesize the protein, leading to decreased production.
Kidney disease, particularly nephrotic syndrome, can also lead to low albumin levels. In this condition, the kidneys’ filtering units, the glomeruli, become damaged, allowing a significant amount of albumin to be lost from the blood and excreted in the urine. Malnutrition or malabsorption syndromes that result in insufficient protein intake or absorption also limit the raw materials the liver needs to produce albumin. Chronic inflammation and infections can contribute to low levels as well.
Conversely, high albumin levels, or hyperalbuminemia, are far less common. This condition is most frequently a result of dehydration. When the body loses a significant amount of fluid, the concentration of solutes in the blood, including albumin, increases. This elevation is typically relative to the reduced volume of plasma rather than an overproduction of the protein itself.
Symptoms and Diagnosis of Albumin Imbalance
The symptoms of an albumin imbalance are most often associated with low levels and are primarily linked to the disruption of fluid balance. The most visible signs are edema in the legs, feet, and ankles, and potentially ascites. Other, less specific symptoms may include feelings of fatigue or general weakness.
Albumin levels are measured through a simple blood test that quantifies the amount of albumin in the serum. This test is often included as part of a routine comprehensive metabolic panel (CMP) or a liver panel, which assesses overall metabolic function and liver health.
It is important to understand that treatment for abnormal albumin levels focuses on managing the underlying cause rather than the albumin level itself. For instance, if low albumin is caused by kidney disease or malnutrition, the treatment plan will address those specific conditions. Correcting the primary health issue typically allows albumin levels to return to a normal range.