Polycystic Ovary Syndrome (PCOS) is a common endocrine disorder affecting reproductive-age women, characterized by hormonal imbalances and irregular menstrual cycles. This condition often leads to endometrial hyperplasia, which is an excessive thickening of the uterine lining (endometrium). PCOS frequently causes a thick uterine lining because hormonal disruption prevents the normal shedding process. The lining continues to grow unchecked. Recognizing this connection is important for managing PCOS and preventing potential complications.
The Hormonal Link: How PCOS Causes Endometrial Thickening
The regular menstrual cycle depends on a precise hormonal balance between estrogen and progesterone, which governs the growth and shedding of the endometrium. Estrogen stimulates the growth and thickening of the uterine lining. Following ovulation, the corpus luteum forms, producing progesterone to stabilize the lining and prepare it for implantation.
A central feature of PCOS is chronic anovulation, meaning the ovaries do not regularly release an egg. Because ovulation is irregular or absent, the corpus luteum does not form, resulting in a lack of progesterone production. Without progesterone to counteract estrogen’s effect and trigger monthly shedding, the endometrium is continuously stimulated to grow.
This situation is often referred to as “unopposed estrogen,” where estrogen continues to drive the proliferation of uterine cells. The lining thickens excessively because it is not shed during a normal menstrual period. Over time, this prolonged stimulation leads to endometrial hyperplasia, where the endometrial glands and stroma multiply abnormally.
This chronic thickening is concerning because hyperplasia is considered a precursor condition. If left unmanaged, the continuous cell overgrowth can lead to changes, increasing the risk of developing atypical hyperplasia or, in rare cases, endometrial cancer. A lack of regular progesterone action is the key mechanism linking PCOS to this gynecological risk.
Recognizing Symptoms and Diagnostic Procedures
The most common signs of endometrial thickening stem from changes in bleeding patterns. Patients with hyperplasia often experience Abnormal Uterine Bleeding (AUB), including periods that are heavier or last longer than usual (menorrhagia). Bleeding can also occur between menstrual cycles, presenting as intermenstrual spotting.
The absence of a period for extended periods (amenorrhea or oligomenorrhea) is another sign, indicating the uterine lining is not being shed. This prolonged absence of bleeding results directly from the anovulation associated with PCOS, allowing the lining to build up. Excessive blood loss over time may also lead to iron-deficiency anemia.
To confirm a suspected diagnosis, a doctor typically begins with a Transvaginal Ultrasound (TVUS). This imaging technique uses sound waves to measure the thickness of the endometrial stripe. While a specific cutoff is not always definitive, an endometrial thickness exceeding a certain limit in a premenopausal patient with PCOS indicates a need for further investigation.
The next step for a thickened lining is usually an Endometrial Biopsy, which provides a tissue sample for microscopic analysis. This procedure is crucial because it confirms the presence of hyperplasia and determines the cell type. Pathologists classify the tissue as hyperplasia without atypia (lower risk) or atypical hyperplasia (higher risk for cancer progression), which guides the treatment plan.
Regulating the Cycle: Treatment for Endometrial Thickening
The primary goal in treating PCOS-related endometrial thickening is to reverse the effect of unopposed estrogen by introducing a progestin. Progestin therapy is effective because it mimics the action of natural progesterone, inducing the shedding of the built-up uterine lining. This process helps to thin the endometrium and restore a healthier tissue state.
A common management strategy involves cyclic progestin therapy, where the hormone is taken for a short duration each month, forcing a withdrawal bleed. Alternatively, continuous progestin therapy delivers the hormone daily to keep the lining consistently thin and prevent further proliferation. Hormonal contraceptives, such as combination birth control pills, are also used for long-term regulation, as they provide both estrogen and progestin to regulate the menstrual cycle.
Another localized treatment option is a hormonal intrauterine device (IUD), which releases progestin directly into the uterus. This method is effective at keeping the endometrium thin with minimal systemic hormonal side effects.
For individuals who are overweight, even a modest weight loss (sometimes as little as 5% of initial body weight) can help improve hormonal balance and reduce circulating estrogen levels. Lifestyle modifications, including diet and regular exercise, can reduce insulin resistance, which is often linked to PCOS hormonal issues. These changes support hormonal therapy by improving the underlying endocrine environment. Regularly inducing a withdrawal bleed significantly lowers the long-term risk of hyperplasia progressing to malignancy.