Uterine fibroids (leiomyomas or myomas) are common, non-cancerous muscular tumors that develop within the wall of the uterus. Their growth is linked to reproductive hormones, specifically estrogen and progesterone, which promote their proliferation. Because fibroids depend on these hormones, they typically appear during a woman’s reproductive years, often causing symptoms like heavy bleeding or pelvic pressure. When a woman enters the post-menopausal phase, the natural expectation is that these growths will shrink as their primary fuel source is withdrawn.
The Typical Change After Menopause
The cessation of the menstrual cycle marks the end of ovarian hormone production. Fibroid tissue is highly responsive to the decline in estrogen and progesterone because it contains a higher concentration of receptors for these hormones than normal uterine muscle cells. When the ovaries reduce hormone output, the stimulus for fibroid growth is removed.
This hormonal withdrawal causes the fibroids to gradually regress in size over time, a process known as atrophy. The decrease in size is often accompanied by relief from previous symptoms, such as pelvic discomfort. For most women, the post-menopausal years bring a natural resolution to fibroid issues. The entire uterus also decreases in size, which further contributes to the overall shrinkage of existing myomas.
Factors That Can Lead to Post-Menopausal Growth
Despite typical regression, fibroids can continue to grow or even appear after menopause under specific circumstances. The most common cause of renewed growth is the introduction of exogenous hormones, often through Hormone Replacement Therapy (HRT). HRT regimens containing estrogen, especially when combined with progestogen, reintroduce the growth factors fibroids need. The fibroid cells react to these externally supplied hormones by reactivating their growth phase, potentially leading to increased size or a return of symptoms.
Hormone Replacement Therapy (HRT)
The degree of potential fibroid enlargement while on HRT depends on the specific hormone formulation, dosage, and duration of use. Women with a history of fibroids must discuss the potential for renewed growth with their physician to select the lowest effective dose. Beyond external hormones, localized estrogen production can occur via aromatization.
Localized Estrogen and Growth Factors
Aromatization primarily occurs in peripheral fat cells, converting androgen precursors into estrogen. This process can provide enough localized hormonal stimulation to prevent complete fibroid atrophy or support continued slow growth. Other substances, such as certain growth factors, can also play a role in maintaining fibroid size independently of ovarian hormones. This non-hormonal persistence or slow enlargement is less common than HRT-induced growth. However, any significant or rapid increase in the size of a uterine mass after menopause is considered an atypical event that warrants immediate medical attention.
Investigating Unexpected Changes
Any new appearance or significant growth of a uterine mass in a post-menopausal woman is treated with caution by medical professionals. The primary concern is ruling out a rare but aggressive form of cancer called uterine sarcoma, particularly leiomyosarcoma. Although fibroids are benign, a rapidly enlarging mass without high hormone levels is suspicious for malignancy.
Diagnostic investigation typically begins with imaging techniques like a transvaginal ultrasound or a pelvic Magnetic Resonance Imaging (MRI) scan. The MRI is useful because it provides detailed information about the mass’s internal structure and blood flow, helping to differentiate between a benign fibroid and a potentially malignant tumor. Unfortunately, even advanced imaging can find it difficult to distinguish an atypical fibroid from a sarcoma, especially if the fibroid has undergone degenerative change.
If imaging is inconclusive, a tissue sample may be necessary, sometimes obtained through an endometrial biopsy or dilation and curettage (D&C). Because sarcomas often originate deep within the uterine muscle wall, a definitive diagnosis frequently requires surgical removal of the mass for complete pathological analysis. Growth after menopause is an abnormal finding that requires prompt, thorough evaluation.