Normal menstruation is characterized by the periodic shedding and bleeding of the endometrium, accompanying the cyclical changes of the ovaries. Abnormal uterine bleeding (AUB) refers to irregular uterine bleeding differing from normal menstruation in terms of cycle frequency, regularity, duration, or volume. The term AUB excludes uterine bleeding occurring during pregnancy, the puerperium, prepuberty, and postmenopause. It represents a symptom complex involving abnormal uterine bleeding rather than a standalone disease and has a significant impact on women's quality of life.
AUB is classified based on its etiology into organic and non-organic categories, divided into nine subtypes. Organic causes include: AUB due to endometrial polyps (AUB-P), adenomyosis (AUB-A), leiomyoma (AUB-L), and endometrial malignancy and atypical hyperplasia (AUB-M), collectively referred to by the acronym PALM. Non-organic causes include: AUB associated with systemic coagulopathy (AUB-C), ovulatory dysfunction (AUB-O), localized endometrial abnormalities (AUB-E), iatrogenic factors (AUB-I), and not otherwise classified cases of AUB (AUB-N), collectively referred to as COEIN. The nine AUB subtypes are summarized as PALM-COEIN.
Ovulatory dysfunction-related abnormal uterine bleeding (AUB-O) accounts for approximately 50% of all AUB cases. AUB-O is further divided into anovulatory and ovulatory subtypes. The former results from anovulation or infrequent ovulation, while the latter is mainly caused by luteal phase dysfunction.
Anovulatory AUB clinically presents with changes in menstrual cycle frequency, regularity, duration, or volume. Severe cases may lead to massive bleeding and significant anemia. This condition is primarily attributed to abnormalities in the hypothalamic–pituitary–ovarian axis and is most common during adolescence and the menopausal transition. It can also occur in reproductive-age women due to stress, polycystic ovary syndrome (PCOS), obesity, hyperprolactinemia, thyroid disorders, adrenal gland disorders, among other factors.
Ovulatory AUB related to luteal phase dysfunction is typically characterized by intermenstrual bleeding (IMB), with clinically recognizable menstrual cycles still present.
AUB-O was previously referred to as "dysfunctional uterine bleeding." However, the International Federation of Gynecology and Obstetrics (FIGO) recommended discontinuing this term in 2011.
To be continued