1, neonatal and childhood hypothyroidism: mothers taking antithyroid drugs during pregnancy (tabazole or propylthiouracil) dose is too large, or pregnant women taking radioisotope iodine inadvertently during pregnancy, or pregnant women taking iodine-containing drugs for asthma treatment or treatment of cardiac rhythm disorders of ethamidium iodofuranone dose is too large, or endemic iodine deficiency or congenital hypoplasia of thyroid gland will lead to neonatal goiter, and severe cases will Cretinism occurs, manifesting severe mental retardation, deafness, and growth retardation. For congenital hypothyroidism, if the treatment can be started within one month after birth, the damage to the nervous system can be reduced; treatment within 3 months, the IQ of the child can be up to 90; 6 months of treatment, the IQ can be reduced to 75, so early diagnosis and early treatment of neonatal hypothyroidism is particularly important. Neonatal hypothyroidism performance: (1) neurological developmental disorders, children with lethargy, poor response, sluggish, will not recognize people, pain perception is reduced, less crying and more sleep, etc., serious cases can also be accompanied by deafness and constipation. (2) Slow growth and development, stagnation of height after 1 to 2 years of age, and obvious backwardness of bone age. (3) Special facial features: large head, short neck, pale and swollen face, wide eye spacing, short nose, thick lips, large and protruding tongue, scanty, yellow and dry hair, hoarse and low cries, indifferent and dull expression, large abdomen with umbilical hernia, and unsteady gait. (4) Low metabolism, poor feeding or milk refusal, abdominal distension, low body temperature, slow heart rate. Normal newborns are born 30 minutes after the serum TSH rises rapidly, three days after the drop to normal, so screening of newborns with hypothyroidism should be 72 hours after birth to take newborns heel blood to determine the TSH, if the TSH is elevated, should be measured T4 to help diagnosis. Hypothyroidism in young children is characterized by growth retardation, mental retardation, less activity, later teething, toddlerhood and speech than children of the same age, and yellowing of the skin, palms of the hands and soles of the feet, but not the sclera. Adolescent hypothyroidism is often accompanied by delayed sexual development, and a few show true precocious puberty. 2, the characteristics of old age hypothyroidism: the onset of old age hypothyroidism is often more insidious, symptoms are often atypical, mucous edema and constipation is often the main complaint of patients with hypothyroidism, resulting in weight gain, swelling of the limbs, the vocal cord edema will cause hoarseness, low voice, anorexia and constipation in the elderly hypothyroidism is very common. 3, subclinical hypothyroidism: serum thyroid hormones (T4, T3, FT4, FT3) is normal, and thyroid stimulating hormone (TSH) is elevated in patients called subclinical hypothyroidism. Since the thyroid hormones are at normal levels, there are no clinical signs and symptoms of hypothyroidism other than goiter with elevated TSH. Subclinical hypothyroidism generally does not require treatment. Thyroid hormone preparation replacement therapy is effective in the treatment of goiter, but goiter will recur after stopping the medication. Clinical hypothyroidism occurs in 5% of patients with subclinical hypothyroidism each year.