Certain medications, birth control pills and digestive conditions, such as irritable bowel syndrome, can cause two menstrual periods in one month, according to WebMD. Irregular menstrual cycles can also be brought on by weight gain or eating disorders such as anorexia nervosa.
Additional medical conditions that may trigger abnormal menstrual periods include cervical cancer; sexually transmitted diseases, such as gonorrhea; thyroid cancer; and ovarian cysts, explains Mayo Clinic. Perimenopause is a natural condition that develops in women who are approaching menopause. During this time, irregular menstrual periods are common. It is important for perimenopausal women to consult with a physician as there are treatments available that can help to minimize uncomfortable symptoms.
Hyperthyroidism, a medical condition that causes the thyroid gland to produce excess amounts of thyroid hormones, can also trigger irregular menstrual periods, explains MedlinePlus. Additional symptoms of hyperthyroidism include concentration difficulties, heavy sweating, intolerance of heat, and sleep disturbances. A variety of factors cause hyperthyroidism, including ovarian cancer and inflammation of the thyroid gland following pregnancy. Hyperthyroidism is treatable with medications, radioactive iodine treatments that halt hormone production, and surgical removal of the thyroid gland. Complications of the condition include abnormal heart rate and osteoporosis, so it is important for women who are experiencing irregular menstrual periods that are accompanied by additional symptoms of hyperthyroidism to consult with a physician.