What Are the Causes of Rapid Weight Loss in Teenagers?

Hyperthyroidism is a medical condition that can cause rapid weight loss in teenagers, especially teenage girls. According to the Family Doctor website, hyperthyroidism, also known as overactive thyroid disease, is a condition in which a person's thyroid gland produces excess thyroid hormone. The thyroid gland is a butterfly-shaped gland that is located in the front of the neck, near the Adam's apple. The thyroid gland produces hormones that regulate metabolism, or the speed of the body's processes. Common signs and symptoms associated with hyperthyroidism include sudden weight loss, rapid heartbeat, increased appetite, anxiety, nervousness, irritability, trembling of the hands and fingers, sweating, changes in menstrual patterns, an enlarged thyroid gland or goiter, muscle weakness, fatigue and depression. The Family Doctor website states that the most common cause of hyperthyroidism is an autoimmune disorder called Graves' disease.

Cancer is a potentially life-threatening disease that can cause sudden weight loss in teenagers. Cancer is collection of over 100 different diseases that can manifest almost anywhere in the body. Cancer occurs when a person's cells begin to grow uncontrollably, forming a mass of cells called a tumor. The Kids Health website states that, although cancer is rare in teens, certain types of cancer tend to manifest in teens more than adults. Osteosarcoma, testicular cancer, Ewing's sarcoma, leukemia, Hodgkin's disease, non-Hodgkin's lymphoma and rhabdomyosarcomas, or soft tissue tumors, occur more often in children and teenagers than adults. Common signs and symptoms associated with cancer include rapid, unexplained weight loss, fatigue, pain, fever, bowel changes and a persistent cough. According to Cancer.net, most American teens with cancer are treated at pediatric oncology centers that have access to the latest treatments.

Anorexia nervosa is an eating disorder that can cause rapid weight loss in teenagers. According to the Cleveland Clinic -- one of the top four hospitals in the United States -- anorexia nervosa is a life-threatening eating disorder in which a person starves herself to lose weight. The diagnosis of anorexia nervosa is made when a person weighs at least 15 percent less than her normal body weight. Rapid weight loss in a person with anorexia nervosa can result in serious health complications, including death. The Cleveland Clinic states that, although anorexia nervosa is most common in teenage girls, teenage boys and adult men and women can also develop this condition. Common signs and symptoms associated with anorexia nervosa include rapid weight loss over several weeks or months, strange eating habits or routines, depression, anxiety, irritability, frequent illness, feelings of worthlessness or hopelessness and decreased cold tolerance.