Overview
Endemic cretinism, also known as endemic cretinism, occurs in areas where severe endemic goiter is endemic, with a general prevalence of 1% to 5% of the population in goiter areas, and up to 5% to 10% in severe areas. The disease is the result of the developmental and differentiation disorders of the brain and central nervous system caused by iodine deficiency and hypothyroidism in the embryonic period and early postnatal period.
Causes
The etiology of endemic cretinism is well established and is the result of severe iodine deficiency during the embryonic and neonatal periods, which affects thyroid hormone synthesis. The predominantly neurologic manifestations of some forms of endemic cretinism are due to severe intrauterine iodine deficiency in the early embryonic period, which impairs neuronal growth and development. In some cases of endemic cretinism with mucous edema, pre-existing neurologic deficits are combined with a reduced ability to synthesize thyroid hormones, suggesting that the thyroid gland itself is dependent on iodine for normal development. Genetic and autoimmune factors have not been proven.
Symptoms
There are 3 types: neurologic type, mucous edema type and mixed type, most of which are mixed.
1. Neurologic type
The height is lower than normal, the thyroid gland is enlarged in 15.3% of cases, most of them are mildly enlarged, and the intelligence is moderately to severely reduced. Apathy of expression, deafness, mental defects, spastic paralysis, strabismus, knee flexion, hyperreflexia of the knee, and pathological reflexes, such as Babinski’s sign, may appear positive. There is no obvious hypothyroidism (hereinafter referred to as hypothyroidism) manifestation.
2. Mucous edema type
There are severe hypothyroidism manifestations, may have the typical face of cretinism, constipation, mucous edema obvious, mental retardation is mild, some can speak, growth retardation, goiter accounted for 28%, sexual development is significantly delayed, tendon reflexes prolonged relaxation time, some patients are familial.
Examination
1. Laboratory examination
Umbilical cord blood T4 is decreased, thyroid stimulating hormone is increased, T3 may be increased.
2. X-ray examination
Distal femoral epiphysis: it should be present at the average of 38 weeks of embryo, and may not be present in cretinism and preterm infants. Pelvic femoral epiphysis: dot-color pattern and deformity, mostly appear within six months after birth. Bone age is backward, the cranial gyrus pressure trace increases, the skull base is short, and the pterygoid saddle is seen to be enlarged.
3. Electroencephalography
Low frequency, irregular rhythm, mostly with paroxysmal bilateral synchronized Q waves, alpha waves may be absent.
Diagnosis
Diagnostic criteria for endemic cretinism:
1. The child is born and resides in a low iodine endemic cretinism area, with mental retardation and varying degrees of mental retardation. There are different degrees of neurological symptoms, such as hearing impairment, speech impairment, motor nerve disorder.
2. Hypothyroidism symptoms/varying degrees of growth and developmental disorders, face of cretinism.
3. Umbilical cord blood T4 is decreased, thyroid stimulating hormone is increased, T3 may be increased. For mucous edema type.
4. X-ray distal femoral epiphysis: should be present at an average of 38 weeks of embryo, can be absent in cretinism and preterm infants. Pelvic femoral epiphysis: point color pattern and deformity, mostly appear within six months after birth.
In addition X-rays show: backward bone age, increased cranial gyrus indentation, short skull base, occasional enlargement of the pterygoid saddle.
Electroencephalogram shows: low frequency, irregular rhythm, mostly paroxysmal bilateral synchronized Q waves, alpha waves may be absent.
Treatment
Endemic cretinism should be diagnosed and treated at an early stage, and thyroid hormone supplementation should be started within 3 months after birth in those with hypothyroidism. Those who are deaf should receive specialized training.
Prevention
Prevention is the mainstay. The government should vigorously implement salt iodization to eliminate endemic goiter, and endemic cretinism will be eliminated as well. Pregnant women can take potassium iodide or iodized oil in the last 3-4 months of pregnancy. Eat more iodized food.