Hypothyroidism has an insidious onset and a long course. In the early stages, there are usually no specific symptoms and signs, and the main manifestations are reduced metabolic rate and decreased sympathetic excitability. As the disease progresses, thyroid hormone deficiency can affect all systems of the body. The thyroid gland itself: can be atrophied or enlarged, and some patients with primary hypothyroidism may also have an enlarged pituitary gland if they are not treated in a timely manner. Skin: The skin is dry and puffy, with mucinous edema. Dermal mucopolysaccharide infiltration and body fluid storage. Digestive system: hypometabolism and weight gain. Poor taste perception, atrophy of the gastric mucosa, and decreased gastric acid secretion. Decreased gastrointestinal motility and constipation. Cardiovascular system: decreased myocardial contractility, decreased cardiac output, and decreased activity tolerance. In severe cases, heart failure and pericardial effusion may occur. Respiratory system: hypoventilation, sleep apnea. Hematologic system: orthocytic and orthochromic anemia, decreased hematocrit. Nervous system: manifestation of indifferent expression, prolonged reflex time, lethargy and drowsiness. Reproductive system: decreased fertility and libido. Menstrual disorders or heavy menstrual flow in women. Other endocrine system: pituitary hypothyroidism may present with hypothyroidism-primary hypoadrenalism (Schmidt syndrome). Therefore, the clinical manifestations of hypothyroidism, on the one hand, do not have characteristic manifestations and only severe cases may present with mucinous edema, on the other hand, the danger is very widespread, with manifestations in all systems.