OVERVIEW

What are the functions of protein?

• Maintain tissue growth, renewal, and repair: Adequate quantity and quality of dietary protein are necessary to sustain the growth, renewal, and repair of tissues and cells.

• Participate in various important physiological functions: Such as catalytic functions, regulatory functions, transport functions, storage functions, protective functions, and maintaining colloidal osmotic pressure in body fluids (e.g., albumin).

• Oxidation for energy: Proteins in the body can generate energy, with about 18% of an adult's daily energy coming from protein.

• Convert into carbohydrates and fats.

What is hypoproteinemia?

A decrease in total plasma proteins, particularly plasma albumin, is referred to as "hypoproteinemia." Clinically, it is often referred to as "hypoalbuminemia."
Hypoproteinemia is not an independent disease but rather a result of various causes leading to negative nitrogen balance (the body loses more protein than it takes in).

What are the main manifestations of hypoproteinemia?

The primary manifestations include malnutrition, affecting human growth and repair functions, leading to symptoms such as emaciation and edema.

What proteins are present in the blood?

Proteins in the blood mainly include plasma proteins and hemoglobin in red blood cells. Plasma proteins consist of albumin, various globulins, fibrinogen, and a small number of binding proteins such as glycoproteins and lipoproteins.

Is hypoproteinemia the same as anemia?

No.

What is the difference between hypoproteinemia and anemia?

Anemia refers to a common clinical condition where the volume of red blood cells in the peripheral blood is reduced, falling below the lower limit of the normal range.

Clinically, hemoglobin concentration is often used to determine the presence or severity of anemia. A decrease in hemoglobin leads to anemia symptoms.

Hypoproteinemia, on the other hand, refers to a reduction in circulating proteins in the blood, which differs from the hemoglobin-related issue in anemia.

What are the harms of hypoproteinemia to the human body?

• In patients with acute or chronic diseases, as well as critically ill patients, serum albumin concentration is negatively correlated with mortality (i.e., lower albumin levels are associated with higher mortality).

• For stroke patients, hypoalbuminemia or hypoprealbuminemia (prealbumin is a type of protein more sensitive in detecting protein malnutrition and liver dysfunction) is often accompanied by malnutrition, functional disability, poor prognosis, and exacerbates neurological deficits during the acute phase.

• Increases the risk of medical complications, such as infections, gastrointestinal bleeding, and diarrhea.

SYMPTOMS

What are the manifestations of hypoproteinemia?

The main clinical manifestation is malnutrition.

Patients experience progressive weight loss, and in severe cases, a cachectic state. Poor appetite, fatigue, weakness, reduced physical strength, gradual decline in responsiveness, and memory deterioration are common. Mild to moderate anemia is frequent, often accompanied by dizziness, and may include orthostatic hypotension and bradycardia.

Edema occurs, and in severe cases, pleural effusion and ascites may develop.

Other symptoms may include decreased sexual function, amenorrhea, osteoporosis, and weakened immune resistance.

Patients with reduced plasma fibrinogen may exhibit bleeding tendencies.

Why do patients with hypoproteinemia develop edema?

Due to decreased albumin levels in the blood, plasma osmotic pressure drops, causing fluid to easily leak from blood vessels into tissues, leading to edema. Mild cases may only involve ankle swelling, while severe cases can include edema in the trunk, eyelids, or even difficulty opening the eyes.

Does hypoproteinemia affect a child's growth and development?

Proteins are crucial components of the human body, playing irreplaceable roles. In children with short-term illness, the impact on growth and development is minimal. However, prolonged hypoproteinemia can hinder growth, resulting in physical and intellectual developmental delays, as well as weakened immune function and reduced resistance to infectious diseases.

What skin changes may occur in hypoproteinemia patients?

Skin lesions in hypoproteinemia are common in severe cases and may include dryness, loss of luster and elasticity, and small scattered erythematous patches that later merge. These changes are often seen on the face and limbs.

How does hypoproteinemia affect hair?

Patients with hypoproteinemia may experience dry, brittle, and dull hair that breaks and falls out easily, becoming sparse. Curly hair may straighten. Dark hair may gradually lighten, turning yellowish-red or even white, with segments of varying shades.

What other diseases are common in hypoproteinemia?

• Fluid and electrolyte imbalances: Hyponatremia, hypokalemia, hypocalcemia, hypomagnesemia, etc.

• Other nutritional deficiencies: Such as vitamin A deficiency.

• Infections and communicable diseases: Weakened overall immune function increases susceptibility to acute and chronic infections, particularly respiratory and gastrointestinal infections. Children are more prone to infectious diseases like measles, tuberculosis, and parasitic infections.

CAUSES

What causes hypoproteinemia?

• Insufficient protein intake or malabsorption: Severe picky eating or dieting can lead to inadequate protein intake; gastrointestinal dysfunction (e.g., post-gastrointestinal surgery) may cause insufficient protein absorption, resulting in hypoproteinemia.
• Impaired protein synthesis: The liver is the site of protein synthesis, and various liver diseases (e.g., cirrhosis) can disrupt protein production.
• Chronic excessive protein loss: Conditions like renal insufficiency may lead to massive proteinuria, causing significant protein loss and hypoproteinemia.
• Accelerated protein breakdown: For example, advanced cancer patients with insufficient nutrient intake may experience increased protein catabolism.

How do hypoproteinemia patients lose protein?

• Conditions like digestive tract ulcers, hookworm disease, and extensive traumatic exudation can cause massive plasma protein loss.
• Repeated abdominal paracentesis or peritoneal dialysis in end-stage renal disease may lead to protein loss through the peritoneum.
• Nephrotic syndrome, malignant hypertension, and diabetic nephropathy can cause massive proteinuria, resulting in urinary protein loss.
• Gastrointestinal malignancies, giant hypertrophic gastritis, protein-losing gastroenteropathy, ulcerative colitis, and regional enteritis may also cause significant protein loss through the digestive tract.

Who is prone to hypoproteinemia?

• People in impoverished areas with predominantly plant-based diets;
• Infants with insufficient breast milk who aren't supplemented with other dairy products, or those fed mainly cereal-based formulas;
• Individuals suffering acute infections, major surgeries, or severe trauma;
• Patients with cleft lip/palate, congenital hypertrophic pyloric stenosis, or achalasia;
• Those with chronic enteritis, bacterial dysentery, severe intestinal parasitic diseases, malabsorption syndrome, or infantile hepatitis syndrome;
• Patients with tuberculosis or malignant tumors;
• Individuals with renal or hepatic dysfunction.

Is hypoproteinemia hereditary?

Hypoproteinemia is generally not hereditary. While certain congenital conditions (e.g., cleft lip/palate, congenital hypertrophic pyloric stenosis, achalasia) may cause hypoproteinemia, this doesn't mean hypoproteinemia itself is inherited.

DIAGNOSIS

How is hypoproteinemia diagnosed?

Hypoproteinemia is diagnosed based on dietary and nutritional status, the aforementioned clinical manifestations, and a total plasma protein level < 60 g/L or a plasma albumin level < 30 g/L.

What tests are needed for patients with hypoproteinemia?

Routine tests include blood tests, urine tests, liver function tests, and kidney function tests. If necessary, cardiopulmonary function tests may also be performed to assess disease severity, guide treatment, and evaluate therapeutic outcomes.

TREATMENT

How to treat hypoproteinemia?

• Address the underlying cause: First, treat the primary condition causing insufficient protein intake, excessive loss, or hypercatabolism.

• Protein supplementation: If there are no contraindications related to the primary disease, protein can be supplemented, and drugs that promote protein synthesis may be considered.

For hypoproteinemia, should protein be supplemented through feeding or injections (how to choose between enteral and parenteral nutrition)?

• For patients with stable conditions and no contraindications related to the primary disease, a high-protein, high-calorie diet can be implemented, with a daily protein intake of 60–80 g and calorie supply exceeding 2,500 kcal/day.

• For those with poor digestive function, liquid or semi-liquid diets can be given, along with sufficient vitamin supplementation.

• For severely ill patients, intravenous amino acid infusion may be administered. For life-threatening hypoproteinemia or impaired liver synthesis, plasma and albumin transfusions can be given.

For hypoproteinemia, is oral supplementation of exogenous albumin effective?

Oral albumin is ineffective as it is destroyed in the stomach, equivalent to eating an egg. Only intravenous albumin infusion can fully exert its effects.

What are the benefits of albumin infusion for hypoproteinemia?

• Rapid reduction of swelling: Quickly increases intravascular albumin concentration, improves plasma colloid osmotic pressure, and relieves tissue edema.

• Fast anti-shock and blood pressure elevation: Acts as an excellent plasma volume expander, rapidly increasing blood volume and maintaining cardiac output in hypovolemic patients.

What are the disadvantages or risks of albumin infusion for hypoproteinemia?

• Excessive albumin infusion does not increase protein synthesis but accelerates protein degradation.

• 10% of intravenously infused albumin moves out of blood vessels within 2 hours, and 100% moves out within 7–10 days (about two-thirds of albumin permeates into interstitial spaces, potentially worsening edema in patients with lymphatic circulation disorders).

• Albumin lacks two essential amino acids (tryptophan and isoleucine).

• Risk of transmitting blood-borne infectious diseases.

• High cost.

• Rapid infusion may cause acute left heart failure in patients with poor cardiac function.

How should hypoproteinemia related to liver disease be treated?

• The fundamental approach is to treat the liver disease, control the condition, and restore liver function as much as possible.

• For severe cases, albumin can be transfused as exogenous supplementation. During non-acute phases, a diet rich in high-quality protein should be provided for endogenous supplementation.

How should hypoproteinemia related to kidney disease be treated?

• Actively treat the primary disease and control conditions like hypertension.

• Dietary therapy. Abnormal protein loss leads to hypoproteinemia, and consuming high-quality protein may help restore normal plasma protein levels.

• Intravenous albumin infusion. Hypoproteinemia often accompanies complications like hyperlipidemia and azotemia, requiring prompt treatment.

How should hypoproteinemia caused by malabsorption be treated?

• Treat the underlying disease.

• Administer intravenous amino acids or albumin if necessary.

• Note: Patients with malabsorption should avoid enteral protein supplementation to prevent increasing gastrointestinal burden and worsening the condition.

Can hypoproteinemia be cured?

Severe cases have a high mortality rate, but with timely treatment, the prognosis is generally good, with most patients recovering fully. Patients should maintain a positive mindset and avoid excessive anxiety, which may hinder recovery.

DIET & LIFESTYLE

How should patients with hypoproteinemia eat?

Patients with simple malnutrition-related hypoproteinemia require a high-protein diet to increase plasma protein levels and protect the liver. This includes high-quality lean meat, fish, dairy, eggs, and soy products, while ensuring a balanced intake of both animal and plant-based foods.

Providing sufficient carbohydrates (such as grains, vegetables, fruits, and sugars) can reduce protein consumption and ease the burden on the liver. Carbohydrates help maintain glycogen levels in liver cells to protect liver function.

It should be noted that special patients, such as those with hepatic encephalopathy, may also have hypoproteinemia but should not consume a high-protein diet. During the acute phase, fasting may be necessary, and dietary intake should follow medical advice.

PREVENTION

None.