Hormonal Imbalance: This is often due to anovulatory cycles, which are common in adolescents, perimenopausal women, and those with polycystic ovary syndrome (PCOS). Hormonal fluctuations can lead to irregular bleeding patterns.

Uterine Fibroids: These are common benign tumors that can cause irregular bleeding, especially if they are submucosal.
Endometrial Hyperplasia: This condition, often associated with unopposed estrogen, can lead to irregular and heavy bleeding.
Intrauterine Device (IUD) Use: Certain types of IUDs, especially those that are non-hormonal, can cause irregular bleeding, especially in the first few months after insertion.
Thyroid Dysfunction: Both hyperthyroidism and hypothyroidism can affect menstrual regularity.

Endometrial Cancer: Although less common, it is crucial to rule out endometrial cancer, especially in postmenopausal women or those with risk factors such as obesity, diabetes, or a family history of cancer.
Pregnancy-Related Complications: Ectopic pregnancy or a miscarriage can present with irregular bleeding and must be considered, especially if there's a possibility of pregnancy.
Invasive Cervical Cancer: Though rare, it can cause irregular vaginal bleeding and should not be overlooked.

Adenomyosis: A condition where tissue similar to the lining inside the uterus grows into the muscular walls of the uterus, leading to heavy and irregular bleeding.
Von Willebrand Disease: A bleeding disorder that can cause heavy and irregular menstrual bleeding.
Uterine Arteriovenous Malformations: Rare vascular anomalies that can cause irregular and potentially life-threatening bleeding.
Ovarian Tumors: Though most are benign, some ovarian tumors can produce hormones leading to irregular bleeding.