Hypothyroidism (underactive thyroid) is a condition in which thyroid gland doesn't produce enough of hormones. Hashimoto's disease is an autoimmune disorder in which your immune system creates antibodies that damage your thyroid gland. Risk factors include age, sex, heridity, other autoimmune disease, radiation exposure. Signs and symptoms of hypothyroidism include Fatigue and sluggishness, Pale, dry skin, puffy face, hair loss, Unexplained weight gain, Depression, Memory lapses.