Hypothyroidism (hypothyroidism or low thyroid) is a systemic disease caused by insufficient synthesis and secretion of thyroid hormones. In the fetal or neonatal period, it is called cretinism; in children, it is called juvenile hypothyroidism; and in adults, it is called adult hypothyroidism. Primary hypothyroidism is caused by diseases of the thyroid gland itself. It is mainly seen in: 1, congenital thyroid deficiency; 2, thyroid atrophy; 3, diffuse lymphocytic thyroiditis; 4, subacute thyroiditis; 5, thyroid destructive treatment (radioactive iodine, surgery); 6, thyroid hormone synthesis disorders (congenital enzyme defects, iodine deficiency or iodine overdose); 7, drug inhibition; 8, infiltrative damage (lymphoid carcinoma, amyloidosis, etc.). Second, serum TSH is reduced in patients with secondary hypothyroidism. It is mainly seen in pituitary disease, pituitary tumor, isolated TSH deficiency; hypothalamic syndrome, hypothalamic tumor, isolated TRH deficiency. Third, peripheral nail reduction is seen. For family hereditary disease, peripheral target tissue uptake hormone function is good, but the cell nucleus receptor dysfunction or lack of, so the physiological effect on the thyroid hormone is weakened. Clinical manifestations I. Adult-type hypothyroidism is mostly seen in middle-aged women, the ratio of men to women is 1:5, with insidious onset and slow development. Typical symptoms are as follows: 1. General manifestations: fear of cold, dry and less sweaty skin, thick, yellowish and cold, sparse and dry hair, brittle and cracked nails, fatigue, drowsiness, poor memory, mental retardation, slow reaction, mild anemia. 2. Weight gain. 2.Special facial features Pale and waxy face, puffy face, dull gaze, loose and swollen eyelids, apathetic expression, few words, hoarseness of speech, slurred speech. 3.Cardiovascular system: slow heart rate, weak heart sound, generalized enlargement of the heart, often accompanied by pericardial effusion in patients with a longer course of the disease. Patients may have obvious lipid metabolism disorders, presenting hypercholesterolemia, hypertriglyceridemia and hypertriglyceridemia, often accompanied by atherosclerosis, the incidence of coronary artery disease is higher than that of the general population, but due to the low metabolic rate of the peripheral tissues, the cardiac blood volume is reduced, and the oxygen consumption of the myocardium is reduced, so angina pectoris and heart failure rarely occur. Sometimes the blood pressure is high, but mostly in diastolic pressure. The electrocardiogram shows low voltage, inverted T wave, widened QRS wave and prolonged P-R interval. 4, digestive system patients with loss of appetite, constipation, abdominal distension, and even paralytic intestinal obstruction. About half of the patients have complete lack of gastric acid. 5.Muscle and joint system: muscle contraction and relaxation are slow and delayed, and muscle pain and stiffness are often felt. Bone metabolism is slow, and bone formation and resorption are reduced. Joint pain, inactivity, a feeling of ankylosis, aggravated by cold, like chronic arthritis. Occasionally see joint cavity effusion. 6, endocrine system, male impotence, female menorrhagia, prolonged untreated may also amenorrhea. The function of tight adenocortex is low, and the blood and urine cortisol are lowered. Primary hypothyroidism can sometimes be accompanied by autoimmune hypoadrenocorticism and (or) type I diabetes mellitus, called Schmidt’s syndrome. Dementia in children with Ketamine disease. Poor appetite, feeding difficulties, no sucking power, quiet, less crying, lethargy, few spontaneous movements, muscle flaccidity, pale, dry skin, cold, thick, hoarse voice, weak tendon reflexes. There is developmental delay. Third, juvenile type hypothyroidism young patients behave like grams of disease. Older children are like adult-type hypothyroidism, and growth and development are affected, pubertal development is delayed, intelligence and poor academic performance. Regardless of the type of hypothyroidism, when the symptoms are severe and not reasonably treated, under certain circumstances, such as infection, cold, surgery, anesthesia or the use of sedatives can be induced coma, especially mucous edema coma. Patients first have drowsiness, body temperature does not rise, even below 35 ℃, blood pressure drops, shallow and slow respiration, weak and slow heartbeat, muscle flaccidity, tendon reflexes disappeared, may be accompanied by shock, cardiac and renal failure and life-threatening. Laboratory examination I. General examination ① blood routine often have mild or moderate anemia, is positive cell positive pigmentation, small cell hypochromic or large cell type. ② Blood glucose is normal or low, glucose tolerance curve is low. Blood cholesterol, triglyceride and β-lipoprotein are increased. Second, the thyroid function tests ① lower basal metabolic rate, often in -30 – 45% below; ② thyroid iodine uptake rate is lower than normal, a flat curve; ③ thyroid hormone serum total T4 lower, often below 38, 6nmol / L, FT4 often <9, 11pmol / L; serum T3 and FT3 can also be reduced to varying degrees, but mildly moderate patients Serum T3 and FT3 can also have different degree of reduction, but mild to moderate patients can sometimes be normal, serum rT3 can be lower than 0,3nmol/L; serum TSH measurement, normal people <4mU/L, in primary hypothyroidism, TSH>5mU/L; secondary hypothyroidism is a significant reduction in the number of patients can be <0,5mU/L. Due to the emergence of high sensitivity thyroid stimulating hormone assay, the TSH excitatory test and the TRH excitatory test has been rarely used. Third, thyroid autoantibodies, the etiology of thyroid autoimmunity, TPOAbTGAb can be increased. Treatment: In addition to transient hypothyroidism (hypothyroidism in the treatment of hyperthyroidism, hypothyroidism caused by other non-thyroidal diseases, etc.), thyroid hormone agents are generally needed for lifelong replacement therapy; transient hypothyroidism is usually treated with a shorter period of time. Thyroid preparations include levothyroxine sodium (L-T4), triiodothyronine (L-T3) and thyroid tablets. Dosage and administration: ① Thyroid tablets, starting dose of 20-40mg/day, increasing by 20mg/day every week until it works. Generally, the swelling subsides first, and then other symptoms improve or disappear successively. After obtaining satisfactory results, find out the appropriate maintenance amount and take it for a long time. L-T40,05-0,1mg/day, increase 0,05mg every 4-6 weeks, and the complete replacement dose is 0,1-0,2mg/day. ③ L-T350-100μg/day, divided into 2 to 3 times, this drug is rapidly absorbed, powerful, unfavorable to sensitive patients with hypothyroidism, generally not routinely applied alone. ④ Children over 1 year old daily dose according to T42,8 ~ 4,4μg/kg orally, or there is an equivalent dose of thyroid tablets (0,1mgT4 equivalent to 40mg thyroid tablets). infants under the age of 1 year old the dose needs to be increased, according to the T410μg/kg orally per day. In addition to thyroid preparation replacement therapy, patients with anemia should be supplemented with iron, vitamin B12, folic acid, or liver preparations, depending on the type of anemia. Those with gastric acid deficiency should be supplemented with dilute hydrochloric acid. Patients with mucous edema coma should be injected intravenously with L-T340-120 μg immediately and 50 μg daily thereafter in 2-3 injections, or with L-T4200 μg immediately and 50 μg daily thereafter, and if there is no injectable agent available, the above drug can be dissolved and injected into the gastric tube every 4-6 hours with the same dosage as above. In addition, attention should be paid to keep warm, give oxygen, keep breathing fluids, infusion should not be too fast, and in case of infection, hydrocortisone can be infused 200-300mg, and antimicrobial infection should be applied.