What causes menstrual irregularities?

Menstrual irregularities can have a variety of causes, including pregnancy, hormonal imbalances, infections, diseases, trauma, and certain medications.

Causes of irregular periods include:

• Perimenopause (generally in the late 40s and early 50s)
• Primary ovarian insufficiency (POI)
• Eating disorders (anorexia nervosa or bulimia)
• Excessive exercise
• Thyroid dysfunction (too much or too little thyroid hormone)
• Elevated levels of the hormone prolactin, which is made by the pituitary gland to help the body produce milk
• Uncontrolled diabetes
• Cushing's syndrome (elevated levels of the hormone cortisol, used in the body's response to stress)
• Late-onset congenital adrenal hyperplasia(problem with the adrenal gland)
• Hormonal birth control (birth control pills, injections, or implants)
• Hormone-containing intrauterine devices (IUDs)
• Scarring within the uterine cavity (Asherman's syndrome)
• Medications, such as those to treat epilepsy or mental health problems

Common causes of heavy or prolonged menstrual bleeding include:

• Adolescence (during which cycles may not be associated with ovulation)
• Polycystic ovary syndrome (PCOS) (bleeding irregular but heavy)
• Uterine fibroids (benign growths of uterine muscle)
• Endometrial polyps (benign overgrowth of the lining of the uterus)
• Adenomyosis (the presence of uterine lining in the wall of the uterus)
• Nonhormonal IUDs
• Bleeding disorders, such as leukemia, platelet disorders, clotting factor deficiencies, or (less common) von Willebrand disease
• Pregnancy complications (miscarriage)

Common causes of dysmenorrhea (menstrual pain) include:

• Endometriosis (uterine lining grows outside the uterus)
• Uterine abnormalities (fibroids or adenomyosis)
• IUDs
• Pelvic scarring due to sexually transmitted infections, such as chlamydia or gonorrhea
• Heavy menstrual flow