What is the normal endometrial thickness in women?

Normal Endometrial Thickness in Women

Normal endometrial thickness varies by menopausal status, with postmenopausal women having a threshold of ≤4 mm considered normal, while premenopausal women have no validated absolute upper limit as thickness varies with menstrual cycle phase. 1

Postmenopausal Women

Normal Range and Clinical Significance

• In postmenopausal women, endometrial thickness ≤4 mm is considered normal and conveys a negative predictive value for endometrial cancer of nearly 100% 1
• A thickened endometrium (≥5 mm) in postmenopausal women generally prompts evaluation by endometrial tissue sampling 1
• The American College of Radiology considers transvaginal ultrasound (TVUS) the first-line screening test for endometrial cancer in the setting of postmenopausal bleeding 1, 2

Risk Assessment

• For asymptomatic postmenopausal women, an endometrial thickness >11 mm is associated with approximately 6.7% risk of cancer 3
• In women with postmenopausal bleeding, the risk of cancer increases significantly with endometrial thickness >5 mm (approximately 7.3% risk) 3
• At a threshold of 4 mm for women with postmenopausal bleeding, sensitivity for detecting endometrial cancer is 90.6%, increasing to 96.9% when using a 3 mm threshold 4

Premenopausal Women

Normal Range and Variations

• Normal endometrial thickness in premenopausal women varies with the phase of the menstrual cycle 1
• There is no validated absolute upper limit cutoff for endometrial thickness in premenopausal women 1
• The endometrium is typically thinnest during menstruation and immediately after, then gradually thickens during the proliferative phase, reaching maximum thickness during the secretory phase

Clinical Implications

• Many studies have shown that endometrial thickness in premenopausal women is not a reliable indicator of endometrial pathology 1
• Even with endometrial thickness <5 mm, endometrial polyps or other pathology may be present in premenopausal women 1
• Abnormal echogenicity and texture of the endometrium has been correlated with significant underlying uterine pathology in both premenopausal and postmenopausal women 1

Factors Affecting Endometrial Thickness

• Body weight and BMI correlate with endometrial thickness in postmenopausal women 5
• Hormone replacement therapy affects endometrial thickness measurements 6
• Women receiving unopposed estrogen or continuous estrogen and progestogen with endometrial thickness between 0.8 and 1.5 cm should undergo endometrial biopsy 6

Clinical Approach to Abnormal Endometrial Thickness

1. In postmenopausal women with bleeding:

   • TVUS is the first-line investigation
   • Endometrial thickness >4 mm requires tissue sampling
   • Consider hysteroscopy with directed biopsy for better diagnostic accuracy 2

2. In postmenopausal women without bleeding:

   • Consider endometrial biopsy if thickness >11 mm due to 6.7% risk of cancer 3
   • Thickness ≤11 mm has extremely low risk of cancer (0.002%) 3

3. In premenopausal women:

   • Interpret endometrial thickness in context of menstrual cycle phase
   • Focus on abnormal echogenicity and texture rather than absolute thickness
   • Consider clinical symptoms when determining need for further evaluation

Remember that while endometrial thickness is an important parameter, it should be interpreted in the context of clinical presentation, patient age, hormonal status, and other risk factors for endometrial pathology.