Anovulatory Cycles: This is the most common cause of irregular bleeding in women of reproductive age, especially in the early years following menarche or before menopause. Anovulatory cycles occur when the ovaries do not release an egg, leading to irregular and unpredictable menstrual bleeding.

Uterine Fibroids: These are common benign tumors that can cause irregular bleeding due to their location, size, and effect on the uterine lining.
Endometrial Hyperplasia: A condition where the lining of the uterus grows too thick, leading to irregular and heavy bleeding. It's more common in perimenopausal women.
Polycystic Ovary Syndrome (PCOS): A hormonal disorder that can cause irregular periods, among other symptoms like acne, excess hair growth, and obesity.
Thyroid Dysfunction: Both hypothyroidism and hyperthyroidism can affect menstrual regularity, leading to irregular bleeding.

Endometrial Cancer: Although less common, it's crucial to rule out endometrial cancer, especially in postmenopausal women or those with risk factors like obesity, diabetes, or a family history of cancer.
Cervical Cancer: Irregular vaginal bleeding can be a symptom of cervical cancer, making it essential for screening and early detection.
Pregnancy Complications: In women of childbearing age, irregular bleeding could be a sign of a pregnancy complication such as a miscarriage or an ectopic pregnancy.

Adenomyosis: A condition where tissue similar to the lining inside the uterus grows into the muscular walls of the uterus, leading to heavy and painful periods.
Bleeding Disorders: Such as von Willebrand disease, which can cause heavy or prolonged menstrual bleeding.
Uterine Arteriovenous Malformations: Rare vascular lesions that can cause irregular and heavy bleeding.
Ovarian Tumors: Although most ovarian tumors do not cause irregular bleeding, some can lead to hormonal imbalances that affect menstrual cycles.