Condition in which too few thyroid hormones are produced, especially common in middle-aged women; in very young children or infants it is known as cretinism. Hypothyroidism can be caused by pituitary disorders, in which too few thyroid stimulants are formed. Other possible causes are iodine deficiency, excessively drastic treatment of hyperthyroidism, or inflammation of the thyroid gland. Lowered content of thyroid hormone in the blood slows down the metabolism, causing some symptoms precisely opposed to those of hyperthyroidism. The patient feels listless and tired, and has difficulty in concentrating. The voice is low and hoarse, and hearing declines. The skin feels dry and cold, and sometimes shows puffy swelling (myxoedema). Nails are thin and fragile, and hair loses its normal gloss. The patient is sensitive to cold; the ambient temperature is never high enough, and extra blankets are needed on the bed even in summer. The heart beats slowly, the patient is often anaemic, and constipated because of intestinal relaxation. In women, menstrual bleeding is heavier and more persistent. In exceptional cases, for example as a result of infection, cooling or the use of drugs to aid sleep, loss of consciousness may occur. Most symptoms develop very gradually, and are sometimes wrongly ascribed to the aging process; a doctor should thus be consulted if a patient suffers increasingly from the symptoms described, or if they worsen. Diagnosis is swiftly achieved by checking blood hormone levels.