In clinical hypothyroidism, the patient has a lower than normal concentration of thyroid hormones with elevated TSH and significant symptoms; in subclinical hypothyroidism, the patient has a normal concentration of thyroid hormones but elevated TSH levels. Hypothyroidism can be secondary to damage to the pituitary gland or hypothalamus, mostly in women. Clinical manifestations] Hypothyroidism caused by surgical resection usually starts more rapidly, while those caused by other causes are insidious and easy to be missed. In adult patients, the symptoms include lethargy, muscle cramps, chills, constipation, weight gain, partial deafness, hoarseness, hair loss, menstrual irregularities in women and impotence in men, and non-depressed mucinous edema, especially in the face, hands, dorsum of the feet and supraclavicular fossa. There may also be bradycardia, cardiomegaly, hypothermia, normocytic normopigmented anemia, hypercholesterolemia, and hyponatremia of the antidiuretic hormone syndrome. Patients often present with depression, slow speech, unresponsiveness, memory loss, and inattention. In severe cases, apathy, withdrawal and dementia may occur. The “mucinous edema psychosis syndrome” may be accompanied by delusions and hallucinations. Subclinical hypothyroidism may present with symptoms of depression and cognitive impairment. It is associated with rapid cycling bipolar disorder, which increases the risk of depression twofold, and can progress to clinical hypothyroidism, especially in women. Hypothyroidism is associated with refractory depression. Treatment] Somatic and psychiatric symptoms can be relieved by thyroxine replacement therapy. Thyroxine doses should be increased gradually, especially in the elderly, in patients with poor health status and in patients with cardiovascular disease. Patients with depressive symptoms usually do not completely disappear until thyroid hormones are normalized, and antidepressants are required for severe depression. psychiatric disorders, mostly manic-like manifestations, may occasionally occur during the initial period of T4 supplementation. Antipsychotics should be given to patients with severe psychiatric symptoms, but it should be noted that phenothiazines can cause hypothermic coma in hypothyroid patients. If left untreated for a long time, cognitive impairment can persist.