Hormone Imbalance: In young women, painful periods are often due to a hormone imbalance that needs to be corrected. Low progesterone in the second half of your cycle causes overgrowth of the lining of the uterus. This overgrowth is the root problem that leads to heavy, painful periods.
Hypothyroidism: Low thyoid function can cause all sorts of problems that are related to hormone imbalance, including low progesterone.
Fibroids: Fibroids are small non-cancerous tumors that grow in the uterus. They are very common in older women, and extremely rare in young women. Fibroids can cause no issues at all, or can be at the root of very painful periods and heavy continuous bleeding.
Endometriosis: Endometriosis is a type of autoimmune disease. Cells from the lining of the uterus (called endometrial cells) travel through the fallopian tubes and out into the pelvis. These cells stick to the bladder, the intestines and the ovaries and cause inflammation. The inflammation is the direct source of the pain.
Each one of these possible underlying root problems have been identified as increased risks for other serious long term illnesses like cancer, cardiovascular disease and infertility. Knowledge about your risks is important for prevention of these diseases.