Metrorrhagia can be defined as 'off schedule' bleeding.  The bleeding, usually of normal or slight amount, occurs at either irregular or regular intervals outside of the normal menstrual flow.  Metrorrhagia is one of many conditions sometimes caused by hormone irregularities, which can be labeled by the more general term, Dysfunction Uterine Bleeding – DUB.

A cycle of 22 to 35 days can be considered of normal length.  Irregularity is any deviation of more than seven days from your normal pattern of bleeding.  Occasional irregularity of menses are very common and pregnancy is the most frequent cause of a late period.  Irregular menstrual bleeding occurs most often in adolescents and in women approaching menopause.

Anovulatory or estrogen breakthrough bleeding is caused by the production of estrogen without normal surges of luteinizing hormone (LH) and secretion of progesterone from the corpus luteum.  This may occur in high or low estrogen states and is the cause of most of the DUB; it occurs at the extremes of the reproductive cycle.  Midcycle spotting is caused by a decrease in estrogen at midcycle following ovulation.  A luteal phase defect is associated with premenstrual spotting or polymenorrhea.  A prolonged luteal phase is caused by extended corpus luteal activity and prolonged progesterone production leading to prolonged cycles or long episodes of menstrual bleeding.

Causes and Development
It can be caused by a hormonal imbalance (Hyperthyroidism or Hypothyroidism); pregnancy disorder; cervical lesions; medications (birth control pills, corticosteroids, hypothalamic depressants, anticholinergics, anticoagulants); uterine fibroids; functional ovarian cysts; polyps; carcinoma of the vagina, cervix, endometrium or ovary; renal or liver disease; coagulation disorders; anabolic steroid use; IUDs or other trauma.