Hormonal Imbalance: This is often the most common cause of irregular menstrual bleeding, particularly in women of reproductive age. Hormonal fluctuations, especially in estrogen and progesterone levels, can lead to irregularities in menstrual cycles, including changes in frequency, duration, and heaviness of bleeding.

Polycystic Ovary Syndrome (PCOS): A condition characterized by multiple cysts on the ovaries, PCOS is associated with hormonal imbalance, obesity, and irregular menstrual cycles.
Uterine Fibroids: Benign tumors that grow in the uterus, fibroids can cause heavy, prolonged, or irregular menstrual bleeding.
Endometrial Hyperplasia: A condition where the lining of the uterus grows too thick, leading to irregular and heavy bleeding.
Thyroid Dysfunction: Both hypothyroidism and hyperthyroidism can affect menstrual regularity by disrupting the body's hormonal balance.

Cancer (Endometrial, Cervical, or Uterine): Although less common, cancer of the reproductive organs can present with irregular menstrual bleeding and must be ruled out to avoid delayed diagnosis and treatment.
Pregnancy Complications: Ectopic pregnancy or a miscarriage can cause irregular bleeding and are medical emergencies.
Bleeding Disorders (e.g., von Willebrand Disease): These conditions can lead to heavy or prolonged menstrual bleeding due to difficulties in blood clotting.

Adenomyosis: A rare condition where tissue similar to the lining inside the uterus grows into the muscular walls of the uterus, leading to painful and heavy periods.
Asherman's Syndrome: A condition characterized by the formation of scar tissue in the uterus, often as a result of uterine surgery, which can lead to irregular menstrual bleeding and infertility.
Hyperprolactinemia: Elevated levels of prolactin can disrupt normal menstrual function, leading to irregular cycles or amenorrhea.