Congenital hypothyroidism, referred to as congenital hypothyroidism, is a disease caused by insufficient synthesis of thyroid hormone or defects in its receptors, resulting in poor brain and bone development, so it is also called cretinism.

According to the location of the lesion, it can be divided into: 1. Primary hypothyroidism: the thyroid gland itself 2. Secondary hypothyroidism: pituitary gland, hypothalamus

According to the cause: 1. Sporadic 2. Endemic

Thyroid hormone synthesis: starting from 12 weeks of pregnancy, if T3 is insufficient, T4 is converted into T3, T4:T3≈8:1

release of thyroid hormone

Regulation of thyroid hormone synthesis and release: the hypothalamic-pituitary-thyroid axis

The main functions of thyroid hormone: 1. Generate heat 2. Promote growth and development (mainly brain and bones) and tissue differentiation 3. Effects on metabolism: promote pro synthesis, increase enzyme activity, promote sugar absorption, glycogen decomposition, and tissue metabolism The utilization of sugar promotes lipolysis 4. Effect on the central nervous system 5. Effect on Vit metabolism 6. Effect on the digestive system 7. Effect on muscles 8. Effect on the blood circulation system

Sporadic congenital hypothyroidism: 1. Hypothyroidism, hypoplasia or ectopy: the main cause 2. Thyroid hormone synthesis disorder: mostly caused by enzyme defects in the synthesis and secretion process of thyroid hormone, resulting in insufficient synthesis 3. Thyroid or target Low organ response: The thyroid gland does not respond to TSH 4. TSH and TRH deficiency (central hypothyroidism): caused by the disorder of TSH secretion by the pituitary gland 5. Maternal factors: the mother takes antithyroid drugs, the mother suffers from autoimmune diseases---exists Anti-TSH antibodies (IgG can cross the placenta)

Endemic congenital hypothyroidism: mostly due to iodine deficiency in the diet of pregnant women, and hypothyroidism in the fetus due to iodine deficiency

Neonatal period: 1. Prolonged jaundice period: normal time - 2 weeks for full term, 4 weeks for premature birth 2. Difficulty feeding 3. Lethargy 4. Umbilical hernia 5. Macroglossia 6. Constipation 7. Low body temperature, cold limbs 8. Low crying

Typical symptoms

endemic hypothyroidism

Inadequate secretion of TSH and TRH

1. Newborn screening: 2-3 days after birth, the dried heel blood of the newborn is tested on a piece of paper with TSH > 15~20mU/L. Serum T4 and TSH need to be retested.

2. Measurement of serum T4, T3, and TSH: confirmed diagnosis = decreased T4, increased TSH, decreased T3/normal

3. TRH stimulation test: T4 & TSH are both low---suspected of insufficient secretion of TRH and TSH---TRH stimulation test

4. X-ray examination: The child’s bone age is obviously behind the actual age---the number of wrist ossification centers = age + 1 (10 in total)

Hirschsprung disease: 1. Constipation, abdominal distension, and umbilical hernia are the main symptoms, but the face, spirit, and crying are normal. 2. Barium enema shows colon spasm and dilation. 3. Rectum muscle biopsy: lack of N-section cells.

Trisomy 21: 1. Special facial features: widely spaced eyes, upward slope of the outer canthus, low bridge of nose, tongue sticking out of the mouth 2. Identification points: normal skin and hair, no myxedema, often accompanied by other congenital malformations

Rickets: 1. Retarded motor development, delayed growth and development 2. Identification points: normal skin, normal intelligence, signs of rickets and X-ray changes

Skeletal developmental disorders: 1. Osteochondrodysplasia 2. Mucopolysaccharidosis 3. All have growth retardation, but have special skeletal manifestations and abnormal metabolic products

Principles: 1. Early diagnosis and early treatment 2. Avoid damage to brain development 3. Once diagnosed, take thyroid preparations for life (except temporary hypothyroidism): (1) L-thyroxine sodium: large starting dose: 10 ~15 ug/kg.d (2) Thyroid tablets