Zinc deficiency in children

Introduction to zinc deficiency in children Zinc plays an important role in many physiological functions of the human body, participates in the synthesis of various enzymes, accelerates growth and development, enhances the ability of wound tissue regeneration, enhances resistance, and promotes sexual function. Zinc deficiency is a syndrome caused by dysfunction of various systemic systems. Zinc is one of the essential trace elements in the body. It is second only to iron in the body and ranks second in the newborn. Of the 3.4 × 10 26 atoms, zinc atoms account for 5.1 × 1020 . Zinc was found to be essential for plant growth as early as the 19th century. In the 1930s, people began to understand the relationship between zinc and animal growth and health, but it was not until 1963 that Praead first raised the issue of zinc deficiency in humans. In the past 20 years, the relationship between zinc's physical growth, development and health has been further emphasized. Zinc has a variety of physiological functions, and zinc deficiency leads to multiple dysfunctions. basic knowledge The proportion of illness: 13% Susceptible people: children Mode of infection: non-infectious Complications: dwarfism

Causes of zinc deficiency in children

Insufficient intake (15%):

The zinc deficiency in food is the main reason for zinc deficiency. The bioavailability of zinc in breast milk is higher than that of milk or soy protein. It is supposed to be related to a low molecular weight component in breast milk. The protein in breast milk is combined with zinc and is considered to be better than milk. (Protein is mainly casein) It is easier to digest and absorb, artificial feeding, not added in time, can also lead to zinc deficiency.

Malabsorption (10%):

Such as suffering from digestive diseases, such as chronic diarrhea, chronic diarrhea, gallbladder fibrosis, intestinal infections and other diseases, can reduce the absorption of zinc, cereals containing phytate or cellulose, can cause zinc absorption, when Excessive divalent ions in food can also affect the absorption of zinc.

Too much loss (12%):

Hookworm disease, malaria can cause repeated blood loss, hemolysis, loss of zinc, trauma, burns and surgery, due to the use of blood zinc mobilization to the wound tissue, resulting in reduced blood zinc, a lot of sweating will also cause excessive loss of zinc .

Disease impact (10%):

Long-term infection, increased zinc requirements during fever, and loss of appetite, if not timely, lead to zinc deficiency, in addition, hereditary malabsorption disease, intestinal acral dermatitis can also cause zinc malabsorption.

Drug impact (8%):

Some drugs, such as long-term use of metal chelators (such as penicillamine, tetracycline, EDTA, etc.), can reduce the absorption rate and biological activity of zinc. These metal chelators are combined with zinc to be excreted from the intestine, resulting in a deficiency of zinc.

Pathogenesis

Protein synthesis barrier

Zinc is involved in the activity and composition of various proteins, nucleic acid synthesis and catabolic enzymes. Therefore, zinc can promote the growth and development of children. Zinc deficiency can cause slow growth, affect cell division, growth and regeneration. Experiments show that after 48 hours of zinc deficiency, There will be obstacles in protein synthesis, cell division, and growth disturbance. Especially in perinatal children, a sufficient amount of zinc is needed to ensure normal development. In childhood, if zinc is severely deficient, it is short and even becomes a dwarf.

2. Impaired immune function

Zinc can promote immune function, and zinc deficiency leads to impaired immune function. Experiments have shown that zinc intake decreases and thymus atrophy in animals, and T cell function declines. Recent intervention experiments suggest that zinc can improve various immune indicators of malnourished children (such as T cell subsets, such as complete parenteral nutrition support (TPN) for children without proper zinc, its natural killer cell activity is reduced, zinc can increase peripheral blood mononuclear cell synthesis of interferon gamma interleukin 1 and 6, tumor necrosis Factor (TNF) alpha and interleukin 2 receptors, as well as concanavalin A-stimulated cell proliferation, physiological levels of zinc can regulate the secretion and production of these immunoregulatory factors, which is very important in monocyte activation, zinc may It is required for the structure and activity of thymosin, a 9-amino acid polypeptide in plasma that stimulates the development of T cells.

3. Loss of appetite

Zinc can promote appetite. Children with zinc deficiency will have loss of appetite and anorexia. This zinc-related anorexia mechanism is more complicated. Possible mechanisms include release of opioids, cholecystokinin or nerves acting on the brain or small intestine. Related to peptide Y.

4. Endocrine gland function changes

Zinc is easy to form a complex with insulin, delaying and prolonging its hypoglycemic effect. At the cellular level, zinc may be related to the release of insulin. Experiments have shown that zinc-deficient animal glandular dysplasia may be associated with decreased secretion of pituitary gonadotropin. Or testosterone production disorders related, other hormones such as estrogen, thyroxine, parathyroid hormone and other secretion changes also have an effect on the concentration of blood zinc.

Prevention of zinc deficiency in children

Breast milk contains high levels of zinc, ranging from 3 to 23 g/L. Breastfeeding should be promoted. Breastfeeding is beneficial for the prevention of zinc deficiency. Zinc is high in fish, meat, animal liver and kidney. Foods containing high zinc and easy to absorb, oysters, cocoa, squid are the highest and easy to absorb; milk and eggs are second; fruits, vegetables, etc. are generally low, when looking at the nutrition of zinc in a food, not only Look at its content and consider the possibility of being actually used by the body. The zinc absorption rate in general food is 40%, and the daily zinc renewal rate in adolescents is 6mg. Therefore, the daily zinc requirement is 15mg, avoiding partial eclipse and avoiding zinc deficiency.

The recommended daily intake of the DRIs of the Chinese Nutrition Society in 2000 is: 1.5mg for infants within 6 months, 8mg for 7 months to 1 year, 9mg for 1 to 3 years, 12mg for 4 to 6 years, 7 to 10 The age is 13.5 mg, and the age of 11 to 17 is 18 to 19 mg (male) and 15 to 15.5 mg (female).

The growth and development of adolescents is very rapid. Each organ is gradually matured, active in thinking, and has the strongest memory. It is an important period of long-term and long-term knowledge in a lifetime. Therefore, nutrition must be adequately supplied. With the development of China's economy, people's living standards have already existed. Great improvement, iron and calcium in mineral elements have attracted people's attention, but there is still not enough understanding of zinc deficiency.

Complications of zinc deficiency in children Complications dwarfism

1. Gnomes: short stature, even becoming a dwarf, showing more than 30% of the standard height of children of the same race, same age, same gender, or adults below 120 cm.

2. Infection: Zinc deficiency leads to impaired immune function and is prone to infectious diseases.

3. Eye disease: night blindness, optic atrophy, poor vision or no visible vision at night or in the dark.

4. Others: Gonadal dysplasia, diabetes, etc., affecting the life of couples after adulthood, severe diabetes can cause secondary complications.

Symptoms of zinc deficiency in children Common symptoms Eating abnormal anorexia immunity Slow growth Hair loss Oral ulcer Optic atrophy Keratitis Diarrhea Night blindness

The clinical manifestations of zinc deficiency are the result of a decrease in the biological activity of one or more zinc.

Slow growth

The early typical manifestation of zinc deficiency in childhood is the slow growth of physiological growth. Zinc deficiency hinders the activity of nucleic acids, protein synthesis and catabolic enzymes, leading to growth retardation in children. The height of zinc-deficient children is often lower than that of normal children. In severe cases, dwarfism can occur.

2. Loss of appetite

After zinc deficiency, it often causes oral mucosal hyperplasia and parakeratosis, which is easy to fall off, and a large number of exfoliated epithelial cells can cover and block the taste buds in the tongue nipple, making it difficult for food to contact the taste buds, not causing taste and appetite, and lacking Zinc has an effect on the synthesis of proteins, nucleic acids, and enzymes, which reduces the activity of zinc-containing enzymes and has a certain influence on the structure and function of taste buds, further reducing appetite.

3.Different food

In children with zinc deficiency, it is often found that there are soil, paper, wall skin and other foreign substances, and the symptoms are improved after zinc supplementation.

4. Decreased immune function

Zinc can enhance the immune function of body fluids and cells, enhance the phagocytic ability and tropism of phagocytic cells, and change the blood infusion and energy metabolism of diseased tissues, improve local and overall functional status, enhance physical fitness and resistance, and reduce infection. When the total amount of zinc is decreased, the immune function of the body is reduced, the immune-related organs such as mesenteric lymph nodes and spleen are reduced by 20% to 40%, the cells with immune function are reduced, the function of T cells is impaired, and the immunity of cells is decreased, thereby reducing The body's defense ability, zinc-deficient children are susceptible to various infectious diseases, such as diarrhea, pneumonia, etc. Experiments have shown that zinc deficiency makes children's immune function impaired, and various immune indicators are improved after zinc supplementation.

5. Wound healing is slow

There is information that zinc treatment can help the healing of wounds, promote the repair of epithelium after burns, reduce the amount of DNA and RNA synthesis after zinc deficiency, reduce the collagen in the granule tissue at the wound, easily destroy the granulation tissue, make the wound, fistula , ulcers, burns, etc. are difficult to heal.

6. Skin damage

The manifestations of skin damage are enteric dermatitis, severe manifestations of various rashes, bullous dermatitis, recurrent oral ulcers, and the characteristics of skin lesions are mostly erosive, symmetrical, often acute dermatitis, can also be expressed For hyperkeratosis, some children showed irregular hair loss, red or light hair, and the hair became darker after zinc treatment.

7. Eye disease

The eye is the organ with the most zinc, and the zinc content of the choroid and retina is the most tissue in the eye, so the eye is very sensitive to the lack of zinc. The lack of zinc causes night blindness. In severe cases, it causes keratitis. In addition, zinc is on the axis. It plays a role in the transport of the pulp and is indispensable for maintaining the function of the optic disc and the nerve. When the zinc is deficient, the axon function is reduced, thereby causing optic nerve disease and optic nerve atrophy.

8. Sexual organ dysplasia

Zinc contributes to the normal development of sexual organs. The concentration of testosterone in the blood is linearly related to blood zinc and zinc. Therefore, when zinc is deficient, sexual organs are poorly developed.

9. Diabetes

Zinc is an important component of insulin. Each insulin molecule contains two zinc. When zinc is deficient, the activity of insulin decreases, the stability of cell membrane structure decreases, and the outer membrane of lysosomes of pancreatic cells ruptures, causing autolysis of cells. Can cause diabetes.

Examination of zinc deficiency in children

It is still difficult to evaluate the nutritional status of zinc in the body. At present, the evaluation criteria of sensitive and specific zinc nutritional status are still insufficient in clinical diagnosis. Determination of serum (plasma) zinc, white blood zinc, red blood cell zinc, zinc, urine zinc and saliva Zinc has been used as an evaluation index for the nutritional status of zinc, but there is no consensus, because it is not a very good evaluation index.

1. Serum (plasma) zinc: At present, the determination of serum (plasma) zinc is a commonly used index, the normal value is 13.8 mol / L (11.5 ~ 22.95 mol / L), because serum zinc is mainly combined with albumin, so Liver and kidney diseases, acute and chronic infections, stress status and malnutrition can all lead to a decrease in zinc concentration. In addition, it is also affected by the environment and the zinc content of the recent diet. When acute zinc deficiency occurs due to increased tissue decomposition, blood zinc levels can still be Within the normal range, various interference factors should be excluded during the measurement.

2. Zinc: Zinc can be used as a reference indicator for chronic zinc deficiency. It has the advantages of no pain in sampling, easy storage and transportation of samples, and simple detection method. However, it is affected by hair growth rate, environmental pollution, washing method and collection site. Therefore, the misdiagnosis rate and the missed diagnosis rate can be as high as 20% to 30%, so it is not a reliable indicator for determining the nutritional status of zinc, and the zinc content is difficult to reflect the recent zinc dynamics, but because the method is simple and easy to accept, it can be used as The detection status of zinc nutrition status and environmental pollution of the group cannot be used as a reliable basis for judging the nutritional status of zinc in individuals.

3. Urinary zinc: urinary zinc can reflect the metabolic level of zinc, the reference value is 2.3 ~ 18.4mol / 24h, but due to the amount of urine and the recent dietary intake of zinc, there are great individual differences, such as blood zinc, zinc The simultaneous determination of urinary zinc has certain reference value.

4. Leukocyte zinc: Although white blood cell zinc is a sensitive indicator of human zinc nutrition level, it requires more blood (at least 5ml) for measurement, and the operation is complicated, so it is not a commonly used indicator.

5. Alkaline phosphatase activity: Since zinc is involved in the formation of the active center of alkaline phosphatase, plasma alkaline phosphatase activity contributes to reflect the nutritional status of zinc, and the activity of alkaline phosphatase decreases in the absence of zinc.

6. Zinc tolerance test: Some authors have also proposed zinc tolerance test to evaluate zinc nutritional status. The determination method is fasting oral zinc 1mg/kg, and the blood zinc concentration peaks in normal people after 2h (8~10mol/L higher than the fasting value). After 6 hours, the patient returned to the fasting level. The peak of zinc deficiency patients was low and returned to the original level in advance. However, the absorption, utilization and storage of zinc all affected the test results, and it was rarely used because of repeated blood draw.

7. Plasma/red metallothionein (MT): In recent years, it has been studied to determine the nutritional status of zinc by radioimmunoassay for plasma and red blood cell MT. For example, when zinc deficiency occurs, plasma and red blood cell MT levels are significantly reduced. Red blood cell MT may be an effective monitoring indicator for zinc supplementation. Plasma MT concentration can sensitively reflect zinc nutrition status of human body. However, other metal elements such as copper and iron can also induce MT synthesis, so its practical value needs further the study.

8. Determination of endocrine function: growth hormone, thyroid hormone, etc. decreased.

X-ray examination, electrocardiogram, EEG, etc. are helpful for diagnosis and differential diagnosis.

Diagnosis and differential diagnosis of zinc deficiency in children

diagnosis

Mainly rely on medical history, clinical manifestations of symptoms and signs and laboratory tests, if necessary, zinc treatment, help to diagnose zinc deficiency disease.

1. History: Careful and detailed medical history, such as whether the baby has a history of weaning or switching to milk, whether the food contains too little zinc, or has a long history of malabsorption.

2. Clinical manifestations: Whether there is growth retardation, decreased sensitivity of taste, loss of appetite or anorexia, ecstasy, and frequent clinical manifestations of infectious diseases.

3. Laboratory examination: laboratory examination is feasible if necessary. At present, the determination of serum (plasma) zinc is a commonly used indicator.

4. Test treatment: If there is a high degree of suspicion of zinc dystrophic diseases, zinc may be properly supplemented, such as symptoms after zinc supplementation, signs are improved or disappeared, and can also be used as an important basis for diagnosis.

Differential diagnosis

1. Dwarfism: When zinc-deficient dwarfism occurs, there is growth stagnation and sexual maturity, and it needs to be differentiated from dwarf diseases caused by other causes such as endocrine diseases.

2. Nutritional deficiency diseases: Different from protein-thermal deficiency, zinc deficiency is short stature, anemia, hepatosplenomegaly, and secondary sexual dysplasia.

3. Diabetes: The activity of insulin is reduced when zinc is deficient, and the rupture of the outer membrane of lysosomes in pancreatic cells causes autolysis of cells, which can cause diabetes, and attention is paid to distinguish between type 1 and type 2 diabetes.

4. Eye disease: Identification of eye diseases such as night blindness, optic nerve disease and optic atrophy caused by other causes.

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