1.General: Patients have a variety of manifestations, lacking specificity, mainly manifested by hypometabolism and hyposympathetic excitation as the prominent, mild early hypothyroid patients can be completely asymptomatic. Typical patients often feel weak, cold, less sweaty, sluggish expression, unresponsive, slow movement, hoarse voice, pale face, puffy face and/or eyelids, broad nose, thick lips and large tongue, and hyperkeratosis of the skin cuticle. The skin appears pale yellow and hair growth is slowed. Peripheral vascular constriction, manifesting pale, cool, dry, thick, flaky, inelastic skin, keratinized hair follicles, sparse hair loss, loss of the outer 1/3 of the eyebrows, brittle and thickened finger (toe) nails. 2. Cardiovascular system: When the thyroid hormone is low, physical examination reveals that the patient has a slow and weak heartbeat, low and dull heart sounds, enlarged heart, bradycardia, swelling of the lower limbs, elevated blood pressure, and reduced pulse pressure difference. Myocardial pseudohypertrophy, electrocardiogram shows low voltage, and sinus bradycardia. About 30% of patients have pericardial effusion and, in severe cases, pleural or abdominal effusion. Hypothyroid heart disease is defined as: (1) hypothyroidism; (2) heart enlargement (ECG showing bradycardia, low voltage, low and/or inverted T waves) except for other causes; (3) cardiac changes that improve or disappear after thyroid hormone replacement therapy. If the patient has pericardial effusion or prolonged systolic time interval (STI), the diagnosis of hypothyroid heart disease is more favorable. 3. Respiratory system: Pulmonary function is mostly normal in hypothyroid patients when they are quiet, but ventilation function is impaired in a few patients, which can cause sleep apnea syndrome in severe cases. Hypothyroidism combined with obesity often has alveolar hypoventilation disorder, and cerebral hypoxia is an important cause of coma in mucus edema. 4, gastrointestinal system: smooth muscle tone of esophagus, stomach, gallbladder, small intestine and colon is weakened, gastrointestinal peristalsis is slow, emptying time is prolonged, gastric acid secretion is reduced, and serum anti-gastric wall cell antibodies are positive. Patients show loss of appetite, abdominal distension, nausea, low gastric acid, and difficulty in defecation. 5. Neuropsychiatric system: Due to hypometabolism and reduced sympathetic excitability, patients show memory loss, especially significant forgetfulness of recent events, inability to concentrate, and reduced comprehension and calculation ability. Older patients with hypothyroidism often have depression, with indifference, depression and silence in the milder cases; in the more severe cases, mental disorders, delusions, hallucinations, disobedience, and even rigidity, dementia and epileptic-like seizures, which should be noticed. 6, muscle and joint: Hypothyroid patients show clinical weakness, muscle pain, tonicity, spasm, edema and hypertrophy, elevated serum CPK, LDH and AST, isoenzymes mainly from the transverse muscle. The Achilles tendon reflex relaxation period is significantly prolonged in hypothyroid patients, but not sensitive enough. Hematologic system: About 25% of hypothyroid patients show anemia, mostly mild or moderate orthochromic or hypochromic microcytic anemia and a few macrocytic anemia. The causes of decreased erythropoiesis are: (1) decreased renal erythropoietin due to decreased metabolism and reduced oxygen consumption; (2) the effect of hypothyroidism on erythropoietic precursors; (3) increased menstrual flow in hypothyroid patients who are mostly female; (4) lack of gastric acid and impaired absorption in the gastrointestinal tract. Some hypothyroid patients (about 12%) also exhibit macrocytic anemia, positive antibodies to gastric lining cells or internal factor antibodies, vitamin B12 or folic acid deficiency, and macrocytic anemia. 8, growth and development: Thyroid hormone has a permissive effect on growth hormone, thyroid hormone deficiency will affect the growth-promoting effect of growth hormone, children with hypothyroidism often show growth retardation, slow epiphyseal healing and delayed bone age. Adolescents with hypothyroidism show delayed sexual development, and a few show true precocious puberty, the cause of which is unknown.