Endemic cretinism is commonly found in areas with severe endemic goiter, where at least one-fifth of the population suffers from goiter. The general prevalence ranges from 1% to 5% of the population in goiter-endemic regions, and can reach 5% to 10% in severe cases. This condition results from iodine deficiency and hypothyroidism during the embryonic period and early postnatal development, leading to impaired brain and central nervous system differentiation.

bubble_chart Etiology

The main disease cause is iodine deficiency during the embryonic stage. Maternal hypothyroidism during pregnancy is a risk indicator for the high incidence of endemic cretinism. Due to iodine deficiency, both the maternal and fetal thyroids competitively uptake limited iodide, thereby affecting thyroid hormone synthesis in both the mother and the newborn. Some cases of endemic cretinism primarily manifest as neurological symptoms, resulting from severe intrauterine iodine deficiency during early embryonic development, which impairs neural growth. If the fetal thyroid later synthesizes thyroid hormones normally, it can prevent the appearance of obvious hypothyroidism after birth. Some cases of myxedematous endemic cretinism occur due to reduced thyroid hormone synthesis on top of pre-existing neurological defects, indicating that normal thyroid development also depends on iodine. Genetic and autoimmune factors have not been confirmed.

bubble_chart Pathological Changes

Unlike sporadic cretinism, the thyroid gland is not absent and can be anatomically near normal. Some show compensatory enlargement, while others exhibit a smaller gland than peers on thyroid scans, often appearing mottled and uneven, suggesting possible thyroid degeneration. The brain may display developmental dysplasia, brain atrophy, middle ear hyperostosis, and other changes. Skeletal development alterations and delays are milder compared to sporadic cretinism.

The disease can be divided into three types: neurological type, myxedematous type, and mixed type. The majority are mixed cases.

1. Neurological type: Height is below normal, goiter accounts for 15.3%, mostly grade I enlargement. Intelligence shows grade III and grade II impairment, totaling 80.6%. Features include apathy, deafness and dumbness, mental defects, spastic paralysis, frequent strabismus, knee joint flexion, hyperactive knee reflexes, and possible pathological reflexes such as positive Babinski sign or elicited Gordon's sign. No obvious clinical manifestations of hypothyroidism are present.

2. Myxedematous type: Severe hypothyroidism is evident, with typical cretinism facies, prominent constipation and myxedema. Intellectual impairment is milder, some can speak, dwarfism is pronounced, growth is delayed, accompanied by goiter (28%). Sexual development is markedly delayed, tendon reflex relaxation time is prolonged, and some cases show familial occurrence.

X-ray findings: Bone age is delayed, cranial convolutional markings are increased, skull base is shortened, and the sella turcica may occasionally be enlarged.

EEG findings: Frequency is low, rhythm is irregular, mostly with paroxysmal bilateral synchronous Q waves, and alpha waves may be absent.

bubble_chart Diagnosis

1. Essential conditions: ① Born and residing in an iodine-deficient endemic goiter area. ② Presence of mental retardation, primarily manifested as varying degrees of intellectual disability.

2. Auxiliary conditions: Neurological symptoms: ① Varying degrees of hearing impairment. ② Varying degrees of speech impairment. ③ Varying degrees of motor nerve impairment.

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A diagnosis of endemic cretinism can be made if the essential conditions are met, along with any one or more of the auxiliary neurological or hypothyroidism symptoms, while excluding a history of childbirth injury, encephalitis, meningitis, or drug poisoning. Early diagnosis may be based on: ① Clinical manifestations characteristic of hypothyroidism; for suspected cases, periodic intelligence and hearing tests should be conducted. ② Umbilical bleeding T₄ levels are decreased, while TSH is elevated; T₃ may be elevated. ③ Distal femoral epiphysis: Normally appears by an average of 38 days in the embryonic cycle, but may be absent in cretinism and premature infants. ④ Pelvic femoral head epiphysis: Stippled and deformed, often appearing within the first six months after birth.

bubble_chart Treatment Measures

Patients with hypothyroidism manifestations should start thyroid hormone supplementation within 3 months after birth, following the same principles as sporadic cretinism. Those with deafness and dumbness should receive specialized training, similar to sporadic cretinism.

bubble_chart Prevention

Prevention is the priority. The government should vigorously promote iodized salt to eliminate endemic goiter, which will consequently eradicate endemic cretinism. In the last 3-4 months of pregnancy, pregnant women can take potassium iodide (1% solution, 10-12 drops daily) or receive a single intramuscular injection of 2ml iodized oil. Consume more iodine-rich foods. Early diagnosis and treatment are essential for endemic cretinism.

1. Sporadic cretinism

2. Pendred syndrome

3. General deafness and dumbness - no intellectual disability, no decrease in urinary iodine, ¹³¹I uptake rate not elevated, no manifestations of iodine deficiency or iodine hunger. For differential diagnosis with other diseases, refer to the differential diagnosis of sporadic cretinism.