Menopause is defined as the point after a woman has gone 12 consecutive months without a menstrual period. This transition marks the end of the reproductive years and involves a significant decline in ovarian hormone production. Any vaginal bleeding occurring after this 12-month milestone is called postmenopausal bleeding (PMB). Since the body is no longer in a reproductive cycle, PMB is never considered normal and always requires a thorough medical investigation.
Defining Postmenopausal Bleeding
Any spotting, light bleeding, or heavy flow occurring after menopause must be evaluated by a healthcare professional. Although the underlying cause is often benign, prompt medical attention is mandatory due to the potential for a serious diagnosis. PMB is the symptom in over 90% of women diagnosed with endometrial cancer, making it a significant warning sign. Therefore, every instance of PMB must be assessed to rule out serious underlying pathology.
Progesterone’s Role in Hormone Therapy
For women who still have their uterus, progesterone plays a protective role when taking estrogen-containing hormone therapy. Estrogen stimulates the growth of the endometrium, the tissue lining the uterus. Unopposed estrogen (estrogen taken without a progestogen) significantly increases the risk of developing endometrial hyperplasia and, eventually, endometrial cancer.
Progesterone is prescribed alongside estrogen to counteract this growth-stimulating effect. Progesterone causes the estrogen-thickened endometrial lining to mature and then shed, preventing the abnormal overgrowth of cells. This controlled shedding process results in the bleeding experienced by many women on hormone therapy. Therefore, progesterone can cause bleeding after menopause, as this shedding is the intended protective mechanism of the hormone.
Bleeding Patterns Based on Progesterone Regimen
The type and timing of bleeding on hormone therapy depend directly on the specific dosing regimen prescribed. The two primary approaches are the cyclic (or sequential) regimen and the continuous combined regimen, which have different bleeding expectations. In a cyclic regimen, estrogen is taken daily, but progesterone is administered only for a short period, typically 12 to 14 days each month. This scheduled dosing causes a predictable, monthly withdrawal bleed, similar to a light period, when the progesterone is stopped.
Continuous Combined Regimen
Conversely, the continuous combined regimen involves taking both estrogen and progesterone every day. The goal of this regimen is to induce endometrial atrophy—a thin, inactive lining that should not bleed. However, light spotting or breakthrough bleeding often occurs during the initial adjustment period, usually within the first six months. If unexpected bleeding continues beyond six months, or if the bleeding becomes heavy, it warrants further medical investigation.
Other Potential Causes of Postmenopausal Bleeding
While hormone therapy is a common cause of PMB, a variety of other conditions must be considered. Genitourinary syndrome of menopause (previously known as vaginal and endometrial atrophy) is the most frequent cause, accounting for approximately 60% of cases. This condition occurs due to the lack of estrogen, causing the tissues of the vagina and uterus lining to become thin, dry, and fragile. This fragility makes them prone to tearing and bleeding even with minor trauma.
Polyps and Hyperplasia
Another common source of bleeding is the presence of polyps, which are usually benign growths on the lining of the uterus (endometrial polyps) or the cervix (cervical polyps). Although not cancerous, these growths can become inflamed or irritated, leading to irregular bleeding or spotting. Endometrial hyperplasia, the excessive thickening of the uterine lining, can also cause bleeding and is considered a precancerous condition.
Endometrial Cancer
The most serious, though least common, cause is endometrial cancer, involving the malignant growth of cells in the uterine lining. Even when a woman takes progesterone, which lowers the risk, other medical conditions like obesity or diabetes can elevate the risk of developing this cancer. Because multiple causes, ranging from benign to life-threatening, present with the same symptom, a medical workup is required to determine the exact origin of the bleeding.
When Immediate Medical Consultation is Necessary
Any instance of postmenopausal bleeding, even a single spot or a pink discharge, requires evaluation by a healthcare provider. The initial assessment typically involves a transvaginal ultrasound to measure the thickness of the endometrial lining. If the lining is thickened beyond a specific threshold, an endometrial biopsy is necessary to collect tissue for analysis and rule out hyperplasia or cancer.
Specific red flags demand an immediate consultation, such as heavy bleeding, large clots, or accompanying abdominal pain. For women on continuous combined hormone therapy, bleeding that persists or starts after the initial six-month adjustment period must also be promptly investigated. A medical evaluation is the only way to ensure the health and safety of the endometrium and determine the underlying cause.