Pediatric iodine deficiency disorders

Introduction to iodine deficiency disorders in children Iodine is an indispensable nutrient for the human body. When the intake is insufficient, the body will have a series of obstacles. Iodine deficiency disease (iodinedeficiencydisease) is caused by the lack of iodine in the natural environment and can cause various diseases. Endemic goiter, endemic cretinism, endemic subclinical cretinism and infertility affecting fertility, premature infants, stillbirth, congenital malformations, etc. are collectively referred to as iodine deficiency disorders. Iodine is an essential component of thyroxine. The thyroid gland uses iodine and tyrosine to synthesize thyroid hormone. Therefore, when the iodine intake is insufficient, the body will have a series of obstacles. Due to the degree and period of iodine deficiency in the body, the body has serious obstacles. The degree is also different. basic knowledge The proportion of illness: acquired iodine deficiency accounted for 1%, congenital about 0.0005% Susceptible people: children Mode of infection: non-infectious Complications: dwarfism

Causes of iodine deficiency disorders in children

(1) Causes of the disease

1. Environmental factors are popular because of the lack of iodine in the soil of most parts of the world, especially the glacial washout and flooding plains, the destruction of soil by human activities, deforestation, soil erosion, and environmental scarcity. There are many reports on iodine and iodine deficiency in mountainous areas. The local goiter in China is also distributed in mountainous areas. It is mainly due to the steep slope of the mountain area, the erosion of rainwater and the loss of iodine from the soil. The iodine deficiency in the Sanjiang Plain of Heilongjiang Province in Northeast China may be due to history. Frequent flooding and active groundwater movements.

Drinking water factor, the content of iodine in some areas is low, which is related to the incidence of iodine deficiency disease. In China's Xi'an, Baoji, Shiquan and Lantian areas, the iodine content in drinking water is low, and the incidence of goiter is also high. .

2. During pregnancy, the iodine intake of pregnant women is insufficient, the concentration of inorganic iodide ions in plasma is reduced, the T3 and T4 produced by the thyroid are less, and the T3 and T4 in the blood are reduced, so that the T3 and T4 of the placenta are reduced, which cannot be satisfied. The needs of the fetus, the growth and development of the fetus, a series of obstacles, the first symptoms of the central nervous system.

3. Dietary factors Dietary factors can also increase the lack of iodine.

(1) Iodine deficiency in the diet: About 60% of the human iodine supply comes from plant foods. For example, iodine deficiency in the soil can lead to insufficient iodine content in plant foods.

(2) Low protein affects the absorption and utilization of iodine: low protein, low energy can reduce serum T3, T4, plasma protein binding iodine (PBI), elevated serum thyrotropin (TSH), low protein, high carbohydrate Can affect the absorption and utilization of iodine by the thyroid gland.

(3) glucosinolates saponins inhibit the iodine organication process: Regarding the dietary factors of iodine deficiency, the current research is more glucosinolate crotonin, which is a component of cassava, such as vegetables Cabbage, cabbage, kohlrabi, and leek also contain hydrolysate of glucosinolate, which inhibits the organicization of iodine.

(4) inhibition of thyroid uptake of iodide: It is widely believed that corn, millet, sweet potato, sorghum and various legumes can release cyanide in the intestine, which is then metabolized to thiocyanate, which inhibits thyroid uptake of iodide. .

(5) High calcium and phosphorus content: Foods with high calcium and phosphorus content can hinder the absorption of iodine, inhibit the synthesis of thyroxine, and accelerate the excretion of iodine.

The above various dietary factors to the body lack of iodine, can not meet the minimum requirements for children to synthesize thyroxine, may appear growth and development backward, such as long-term iodine deficiency, decreased thyroid hormone levels, increased secretion of TSH in the pituitary gland, increased thyroid volume, diffuse Goiter.

4. Drug factors Thiourea anti-thyroid drugs, tetracycline, sulfonamides, imidazoles and other drugs can interfere with the iodine iodization process, but also certainly cause goiter.

(two) pathogenesis

The physiological function of iodine is mainly used as a synthetic raw material for thyroid hormones, so the physiological function of iodine is also manifested by the action of thyroxine.

1. Promote physical growth Postnatal physique growth and skeletal maturation depend on normal levels of thyroid hormone secretion, which promotes growth and sexual development of height, weight, bones and muscles during child development. When iodine is insufficient, these can be A delay has occurred.

2. Participation in energy metabolism Thyroid hormone is also mainly involved in the energy metabolism of the body cells. The most familiar indicator is the basal metabolic rate. Thyroid hormone can enhance the body's basal metabolic rate, promote the catabolism of substances, increase oxygen consumption, generate energy, and maintain basics. Life activities, keep body temperature.

3. Nervous system development Thyroid hormone can affect the growth, migration and dendritic development of brain nerve cells, it can also promote the growth and maturation of peripheral tissues, in the critical period of brain tissue development (from the beginning of pregnancy to 2 years after birth) The development of the nervous system depends on the presence of thyroxine, the proliferation of neurons, differentiation and myelination, especially the establishment of dendrites, dendritic spines, synapses and neural connections. The lack of thyroxine is involved. Lead to brain developmental disorders leading to permanent, irreversible brain insufficiency.

Insufficient iodine intake during pregnancy, iodine concentration in pregnant women is reduced, although the thyroid gland in pregnant women is in a state of increased compensatory iodine absorption rate, but the thyroid gland produces less T3, T4, and most of the blood T3, T4 and thyroid gland Binding globulin and other binding exist, and the combined T3, T4 can not pass the placental barrier, so that T3, T4 through the placenta can not meet the needs of the fetus, the fetus grows and develops a series of obstacles, the central nervous system first symptoms.

4. Participation in the regulation of pituitary The normal physiological function of the pituitary depends on the support and guarantee of thyroid hormone, such as the synthesis of thyroid hormone, insufficient release, weakened negative feedback inhibition of pituitary gland, excessive secretion of thyroid stimulating hormone (TSH) in the pituitary gland and thyroid tissue Hyperplasia, gland enlargement.

After birth (especially after weaning), children can take iodine directly from the diet, so iodine deficiency has improved, but if the diet continues to lack iodine, can not meet the minimum requirements for children to synthesize thyroxine, then there is growth and development, Such as long-term iodine deficiency, thyroid tissue from the process of compensation to pathological damage, iodine deficiency, decreased thyroid hormone levels, increased secretion of TSH in the pituitary gland, stimulation of thyroid follicular epithelial hyperplasia, hyperplastic follicles in thyroid tissue, follicular epithelium Increased, small follicular cavity, reduced gel storage, increased thyroid volume, enhanced function, such as prolonged or repeated, diffuse goiter.

Prevention of iodine deficiency disorders in children

Eugenics experts pointed out that if pregnant women do not pay attention to the intake of iodine-containing food during pregnancy, especially pregnant women living in iodine-deficient areas, it will lead to fetal iodine deficiency, so the iodine department during pregnancy will prevent this disease.

Pediatric iodine deficiency complications Complications, dwarfism

1. Dwarfism is poor in growth and development and can be dwarfism.

2. The nervous system has brain developmental disorders, leading to mental retardation, permanent, irreversible brain dysfunction, hoarseness, mental defects, strabismus, paralysis or paralysis.

3. Sexual developmental disorders.

Symptoms of iodine deficiency disorders in children Common symptoms Iodine deficiency, constipation, constipation, goiter, goiter, mucinous edema, hoarseness, hypothyroidism, hypothyroidism, strabismus, hyperreflexia

The clinical manifestations of iodine deficiency disorders depend on the degree of iodine deficiency, the developmental stage of the body during iodine deficiency, and the body's responsiveness to iodine deficiency or compensatory anaerobic tolerance, such as iodine deficiency in embryonic brain tissue development. The critical period (from the beginning of pregnancy to 2 years after birth) mainly affects mental development, and there are physical development and sexual development disorders, that is, cretinism. If iodine deficiency is in childhood, goiter can occur.

1. Endemic hypothyroidism can be divided into 3 types: nerve type, mucinous edema type, mixed type, most children show mixed type.

(1) Neurological type: moderate and severe mental decline, mild thyroid enlargement, normal height, indifferent expression, hoarseness, more mental defects, more strabismus, sputum or paralysis, knee flexion, knee reflex Pathological reflex can occur, thyroid function is normal or mildly low.

(2) Mucinous edema type: mild mental retardation, some can speak, pygmy state is obvious, growth and development are backward, there is goiter and severe hypothyroidism, typical face, constipation and mucinous edema More prominent, some patients have familial morbidity.

(3) Mixed type: The clinical manifestations of both, the clinical manifestations of two types of endemic hypothyroidism.

2. Goiter according to whether there are nodules in the goiter, divided into the following 3 types:

(1) diffuse type: the thyroid is evenly enlarged, and the nodules are not touched.

(2) Nodular type: one or several nodules are touched on the thyroid gland.

(3) Mixed type: Touch one or several nodules on the diffuse enlarged thyroid gland.

If the thyroid gland is swollen, it can cause cough and dyspnea caused by compression of the trachea. Pressing the esophagus can cause difficulty in swallowing. Compression of the recurrent laryngeal nerve causes hoarseness. Post-sternal goiter can cause venous return of the head, neck and upper extremities to be blocked. Cyanosis, edema.

3. Subclinical patients

(1) Hypothyroidism: In addition to obvious hypothyroidism and endemic goiter, there are many subclinical patients. De Quarrain and Wegelin first use hypothyroidism to describe subclinical patients and do As specified below: if there is suspicious hypothyroidism, suspicious mental retardation or both, as long as one of them, consider hypothyroidism.

(2) Subclinical physiology developmental lag syndrome: mainly the height and weight are lower than normal children, some physiological examination indicators such as grip strength, lung capacity and blood pressure are also low, a few people have mild epiphyseal development, backward sexual development Generally not obvious.

Examination of iodine deficiency disorders in children

1. Evaluation of iodine nutritional status It is customary to evaluate the nutritional status of iodine according to the discharge of urinary iodine. The urinary iodine of children is less than l00g/24h, suggesting iodine malnutrition.

2. Hormone levels include levels of T3, FT3, T4, FT4, and TSH, with T4 and FT4 decreasing and TSH elevation being an indication of iodine deficiency.

3. Thyroid scan can be close to normal anatomy, or compensatory enlargement, or less than the same age, often manifested as uneven pitting, children with thyroid enlargement rate greater than 5%, suggesting iodine malnutrition, but goiter It may be caused by iodine deficiency in the past. After iodine deficiency is corrected, the goiter may take several months or even years to resolve, and urinary iodine is at a normal level.

4. X-ray inspection

(1) Bone age is backward: the bone age is backward, and the osteogenesis center and the epiphysis cannot appear on time.

(2) Skull: The cerebral gyrus is increased, the skull base is short, and the butterfly saddle is occasionally enlarged.

5. The EEG frequency is low and the rhythm is not complete. Most of them have paroxysmal bilateral synchronous Q waves, but no a wave.

6. Brain CT has brain atrophy.

Diagnosis and differential diagnosis of iodine deficiency disorders in children

diagnosis

1. Diagnostic criteria for endemic hypothyroidism

(1) Environmental factors: born, living in areas with low iodine endemic goiter.

(2) Neurological and psychiatric symptoms: mental and neurodevelopmental disorders, mainly manifested in varying degrees of mental retardation, speech disorders and motor neurological disorders.

(3) Typical face and developmental disorders: different degrees of physical and sexual developmental disorders, special typical face.

2. The diagnostic criteria for endemic goiter reside in the endemic area of endemic hypoiodine goiter disease, with clinical manifestations of goiter and related compression symptoms, other thyroid diseases excluding goiter, laboratory tests for urine Low iodine, TSH in plasma can be increased to varying degrees, plasma T4, T3 concentration is normal, but severe patients with T4 is lower than normal, T3 is slightly higher, thyroid scan can also be seen diffuse or nodular goiter.

Differential diagnosis

1. Brain damage excludes birth injury, encephalitis, meningitis and drug poisoning, etc., living in the iodine-deficient area of the natural environment, showing a variety of iodine intake, the body will have a series of obstacles, plus laboratory tests Indicators, no birth injury, encephalitis, meningitis and drug poisoning, can be diagnosed as endemic hypothyroidism,

2. Other causes of hypothyroidism exclude other causes of hypothyroidism, such as:

(1) thyroid hormone production disorders: belonging to autosomal genetic diseases, patients often have a family history, goiter is diffuse, soft, rarely developed into nodular, iodine organic dysfunction can be diagnosed with potassium perchlorate excretion test, normal Value 2h excreted <5%, patients often >10%,

(2) Hormone resistance: syroid hormone resistance syndrome (SRTH) is also called thyroid hormone insensitivity syndrome (THIS), the disease is familial More common, there are a few scattered cases, accounting for about 1/3, the age of onset is mostly in children and adolescents, the youngest is newborn, both men and women can be sick, clinical manifestations of T4 and T3 continue to rise, while TSH is normal The patient has no drug, non-thyroid disease and thyroid hormone transport abnormality. The most specific manifestation is that after giving the patient a super physiological dose of thyroid hormone, it can not inhibit the elevated TSH to normal, and there is no response of peripheral tissues to excessive thyroid hormone. ,

3. Slow-onset inflammation and Graves' disease, slow-onset inflammation and Graves' disease are autoimmune thyroid diseases, which are caused by lymphocytes secreting thyroid stimulating hormone receptor antibody (TSB receptor antibody, TRAb). TRAb stimulates thyroid follicular hyperplasia and hyperfunction. Clinical manifestations of toxic diffuse goiter, invasive eye disease and sputum mucinous edema, elevated thyroid autoantibodies TGAb and TPOAb support the diagnosis of chronic thyroiditis,

4. Deafness, general deafness, no mental retardation, no reduction in urinary iodine, T131I is not high, no other iodine deficiency.

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