The blood can be divided into two basic parts: the blood cells and the watery component called plasma. The cells are mostly red blood cells that carry oxygen, plus white blood cells of the immune system and platelets to stop bleeding. The plasma contains protein. Levels can be low in certain disorders, and the concentration of protein in the blood measured and tracked to monitor the severity of the disorder.
Protein Losing Enteropathy
Protein enters the body from the diet and is broken down by the intestines into amino acids and absorbed. A protein losing enteropathy is a category of diseases of the gastroinstestinal tract that results in the loss of protein from the body through the stool. Some causes include Crohn's disease, celiac disease, short bowel syndrome, enteropathy caused by NSAIDs such as ibuprofen and infection with giardia.
Liver Disease
The liver absorbs amino acids supplied to it from the blood vessels of the intestine. It uses the amino acids to synthesize the body's own proteins. Diseases that damage the liver cells will decrease the ability of the liver to synthesize protein for the blood, and levels will decline. Steatohepatitis in which the liver cells are replaced by fat, cirrhosis from hepatitis, alcohol or inherited diseases such as hemochromatosis, a disease of iron overload, will result in low protein.
Kidney Disease
The kidneys have several functions, including filtering the blood. Blood flows through the kidneys, and the small blood vessels, called glomeruli, in the kidneys act like a mesh, net or sieve. They keep large proteins and blood cells in the blood vessels. The liquid component of blood and small molecules move into the tubes of the kidneys, called nephrons. The nephrons can reabsorb chemicals into the blood that the body needs and pass the rest into the urine. In some forms of kidney disease, collectively called the nephrotic syndrome, protein is lost into the urine.
Malnutrition
Since the diet is the source of protein for the body, a lack of dietary protein can result in low blood levels. The body will compensate at first by breaking down protein in the body, mostly in the skeletal muscle; however, the body will be able to compensate in this way for only so long, and the results of protein deficiency will manifest. These can include irritability, tissue damage, a weakened immune system and fatigue.
References
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar, et al.; 8th Ed 2009
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci, et al.; 17th Ed 2008
