What are the causes of endometrial (uterine lining) thickening?

From the Guidelines

Endometrial thickening should be evaluated with transvaginal ultrasound (TVUS) as the first-line screening test, particularly in postmenopausal women, where an endometrial thickness of 4 mm or less conveys a negative predictive value for cancer of nearly 100% 1.

Evaluation of Endometrial Thickening

When evaluating endometrial thickening, it is essential to consider the patient's menstrual status and symptoms. In premenopausal women, normal endometrial thickness varies with the phase of the menstrual cycle, and there is no validated absolute upper limit cutoff for endometrial thickness 1. However, in postmenopausal women, an endometrial thickness of 5 mm or more generally prompts evaluation by endometrial tissue sampling 1.

Diagnostic Approach

The diagnostic approach to endometrial thickening typically involves TVUS, which can detect both benign endometrial or myometrial pathologies such as endometrial hyperplasia, polyps, adenomyosis, or leiomyomas 1. TVUS should be combined with transabdominal US whenever possible to fully assess the pelvic structures. Although TVUS is sensitive for the evaluation of endometrial thickness, it cannot reliably determine the etiology of endometrial thickening 1.

Treatment and Management

Treatment of endometrial thickening depends on the underlying cause and may include hormonal therapy, such as progestins or combined hormonal contraceptives, or surgical procedures in cases of hyperplasia or cancer 1. It is crucial to note that endometrial thickening can result from normal hormonal fluctuations, hormone therapy, certain medications, or pathological conditions, including polyps, hyperplasia, or endometrial cancer, which is why proper medical assessment is essential.

Key Considerations

• In postmenopausal women, an endometrial thickness of 5 mm or more requires further investigation 1.
• TVUS is the first-line screening test for endometrial cancer in postmenopausal women 1.
• Endometrial tissue sampling is necessary to determine the etiology of endometrial thickening in postmenopausal women with an endometrial thickness of 5 mm or more 1.
• Treatment depends on the underlying cause of endometrial thickening and may involve hormonal therapy or surgical procedures 1.

From the FDA Drug Label

Whether this will provide protection from endometrial carcinoma has not been clearly established Studies of the addition of a progestin product to an estrogen replacement regimen for seven or more days of a cycle of estrogen administration have reported a lowered incidence of endometrial hyperplasia Morphological and biochemical studies of endometrial suggest that 10–13 days of a progestin are needed to provide maximal maturation of the endometrium and to eliminate any hyperplastic changes.

The use of medroxyprogesterone acetate may help to prevent endometrial hyperplasia, which can be a precursor to endometrial thickening. However, the exact effect of medroxyprogesterone acetate on endometrial thickening is not clearly established.

• The medication may help to mature the endometrium and eliminate hyperplastic changes.
• The relationship between medroxyprogesterone acetate and endometrial carcinoma is also not clearly established 2.

From the Research

Endometrial Thickening

• Endometrial thickness (ET) is a significant factor in the diagnosis of endometrial cancer, and transvaginal ultrasound (TVUS) is an accurate and non-invasive technique for measuring ET 3.
• There is no consensus on the cutoff value for normal ET in postmenopausal women, either symptomatic or asymptomatic 3, 4.
• For postmenopausal women with postmenopausal bleeding (PMB), TVUS is necessary to evaluate ET as an indicator for endometrial biopsy 3.
• In asymptomatic postmenopausal women, the cutoff value of ET that warrants investigation is still debated 4, 5.
• A study found that an endometrial thickness of 4 mm or more may be a threshold for further investigation in postmenopausal women with PMB 6.
• Another study suggested that a threshold of 3 mm or more could maximize sensitivity, but this would also increase the number of unnecessary investigations 6.
• In asymptomatic postmenopausal women without vaginal bleeding, about 10% have a sonographic endometrial thickness of 5 mm or more, and conservative management may be appropriate in these cases 7.

Diagnostic Approaches

• TVUS is the initial best modality for assessing ET or aberration 4.
• Hysteroscopy may be necessary for further evaluation and diagnosis in cases with thickened endometrium, especially in postmenopausal women with PMB or those at high risk of endometrial cancer 3, 5.
• Saline contrast sonohysterography (SCSH) may be used to evaluate intrauterine focal lesions in women with endometrial thickness of 5 mm or more 7.

Risk Factors and Management

• Postmenopausal bleeding remains the most reliable indicator of endometrial pathology 6.
• The presence of risk factors, such as hormone replacement therapy (HRT) or tamoxifen use, may influence the management of endometrial thickening 4.
• Endometrial sampling may not be routinely performed in asymptomatic postmenopausal women without bleeding, but may be considered on a case-by-case basis based on risk factors 3.