Albumin – Functions, Normal Values and Significance
Albumin is the most abundant protein in human blood, playing a key role in transporting substances and maintaining the fluid balance within the body.
Things worth knowing about "Albumin"
Albumin is the most abundant protein in human blood, playing a key role in transporting substances and maintaining the fluid balance within the body.
What is Albumin?
Albumin is the most abundant protein in human blood plasma, accounting for approximately 55–60% of all plasma proteins. It is produced exclusively in the liver and has a half-life of about 20 days. Albumin is a water-soluble, globular protein with a molecular weight of approximately 66,500 daltons.
Biological Functions
Albumin performs several vital functions in the human body:
- Transport function: Albumin binds and transports numerous substances through the bloodstream, including fatty acids, hormones, bilirubin, calcium, medications, and other metabolic products.
- Maintenance of colloid osmotic pressure: Albumin plays a key role in keeping fluid within blood vessels and preventing it from leaking into surrounding tissues. Low albumin levels can lead to edema (fluid retention).
- Buffering function: Albumin contributes to regulating the acid-base balance in the blood.
- Antioxidant properties: Albumin has antioxidant effects and protects cells from oxidative stress.
Normal Values and Measurement
Albumin levels in the blood are determined through a simple blood test. Normal values for adults typically range between 3.5 and 5.0 g/dL. Values may differ slightly in newborns and older adults. Albumin measurement is part of routine blood and liver function testing and serves as an important marker for nutritional status and liver function.
Causes of Low Albumin Levels (Hypoalbuminemia)
A decreased albumin level, known as hypoalbuminemia, can have various causes:
- Liver disease: Since albumin is produced in the liver, conditions such as cirrhosis or hepatitis reduce its production.
- Malnutrition or undernutrition: Insufficient protein intake reduces albumin synthesis.
- Kidney disease: In nephrotic syndrome, large amounts of albumin are lost through the urine.
- Chronic inflammation: Inflammatory conditions suppress albumin synthesis in the liver.
- Burns or severe injuries: Loss of body fluids causes albumin levels to drop.
- Malabsorption syndromes: Conditions such as Crohn's disease or celiac disease can impair protein absorption.
Causes of High Albumin Levels (Hyperalbuminemia)
Elevated albumin levels are less common and usually occur in cases of dehydration, where the blood becomes concentrated, raising the levels of all blood proteins. This is generally not an independent condition but rather an indicator of fluid deficiency.
Symptoms of Albumin Deficiency
Low albumin levels can cause the following symptoms and signs:
- Edema (fluid retention), especially in the legs and abdominal cavity (ascites)
- Fatigue and general weakness
- Muscle wasting
- Poor wound healing
- Increased susceptibility to infections
Diagnosis
A change in albumin levels is diagnosed through a blood test. If albumin loss through the kidneys is suspected, a urine test (albumin in urine, known as microalbuminuria) may also be performed. As part of the diagnostic workup, total protein concentration in the blood is often measured to provide a comprehensive picture of protein metabolism.
Clinical Significance and Treatment
Albumin serves as an important clinical marker for:
- The nutritional status of patients
- Liver function
- The severity of chronic diseases
- The risk of complications during surgery or intensive care
Treatment of albumin deficiency depends on the underlying cause. In severe cases, albumin can be administered as an infusion (e.g., in liver cirrhosis with ascites or following major surgery). Long-term management involves a protein-rich diet and treatment of the underlying condition.
Albumin in Medicine and Pharmacy
Human serum albumin is also used as a medicinal product, for example in the treatment of shock, severe drops in blood pressure, or certain liver diseases. In addition, albumin is used in pharmaceutical research as a carrier molecule for drugs, as it is able to bind and transport active substances in a targeted manner.
References
- Loscalzo J, Fauci A, Kasper D et al. - Harrison's Principles of Internal Medicine, 21st edition, McGraw-Hill Education, 2022.
- Albumin Human - Summary of Product Characteristics, European Medicines Agency (EMA), www.ema.europa.eu (accessed 2024).
- Arroyo V, Garcia-Martinez R, Salvatella X. - Human serum albumin, systemic inflammation, and cirrhosis. Journal of Hepatology, 2014; 61(2): 396-407. PubMed PMID: 24816047.
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