From the Guidelines
Normal endometrial thickness is less than 5 mm in postmenopausal women and varies with the phase of the menstrual cycle in premenopausal women, with no validated absolute upper limit cutoff. When evaluating endometrial thickness, it is essential to consider the patient's menstrual cycle phase and menopausal status. In premenopausal women, the endometrium thickness varies throughout the menstrual cycle, and even if the thickness is <5 mm, endometrial polyps or other endometrial pathology may be present 1. In postmenopausal women, an endometrial thickness of 4 mm or less conveys a negative predictive value for cancer of nearly 100% 1. Some key points to consider when evaluating endometrial thickness include:
- Endometrial thickness is typically measured via transvaginal ultrasound (TVUS), which provides the most accurate assessment 1.
- TVUS is sensitive for the evaluation of endometrial thickness but cannot reliably determine the etiology of endometrial thickening 1.
- Abnormal echogenicity and texture of the endometrium have been correlated with significant underlying uterine pathology 1.
- 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.
- For postmenopausal women, a thickened endometrium (≥5 mm) generally prompts evaluation by endometrial tissue sampling 1.
From the Research
Normal Endometrial Thickness
- The normal range of endometrial thickness in postmenopausal women varies, but a thickness of less than or equal to 11 mm is generally considered normal 2.
- A study found that the mean endometrial thickness in asymptomatic postmenopausal women was 2.3 mm in the first 5 years after menopause, decreasing to 1.8 mm from 5 to 13 years after menopause, and then increasing slightly to 2.0 mm after 13 years 3.
- Another study found that the mean endometrial thickness in postmenopausal women with vaginal bleeding was 18.02 mm, with a range of 5 to 64 mm 4.
- A threshold of 4.5 mm was used in a study to identify women with postmenopausal bleeding who may be at risk for endometrial cancer 5.
- It is essential to note that endometrial thickness can vary depending on the individual and the timing of the measurement, and that other factors such as vaginal bleeding and ultrasound findings should also be considered when evaluating endometrial health 2, 6, 3, 4, 5.
Factors Affecting Endometrial Thickness
- Age: Endometrial thickness tends to decrease with age in postmenopausal women 3.
- Menopausal status: Endometrial thickness can vary depending on the time since menopause 3.
- Vaginal bleeding: The presence of vaginal bleeding can be a sign of abnormal endometrial thickness 2, 4, 5.
- Hormone replacement therapy: Unopposed estrogen can increase the risk of endometrial hyperplasia and cancer 6.
- Ultrasound findings: Ultrasound can be used to evaluate endometrial thickness and morphology, and to identify potential abnormalities such as polyps or cancer 4, 5.