What are the maximum and minimum thicknesses of normal endometrium?

Under normal circumstances, the endometrium ranges from a maximum thickness of 10 mm to a minimum of 5 mm. However, endometrial thickness varies with the physiological cycle, which typically includes the follicular phase, luteal phase, and menstrual phase—each associated with different endometrial thicknesses.

1. Follicular Phase

During this phase, the endometrium is relatively thin, approximately 1–2 mm. It gradually thickens over time, reaching 3–5 mm between days 11 and 14 of the menstrual cycle. If the thickness exceeds 5 mm, it may be due to medications such as estradiol valerate tablets or progesterone soft capsules, or conditions such as endometrial hyperplasia or endometrial polyps.

2. Luteal Phase

The luteal phase corresponds to the secretory phase of the menstrual cycle, occurring on days 15–28. Under the influence of progesterone and estrogen, the endometrium continues to thicken as it transitions from the follicular to the luteal phase, potentially reaching up to 10 mm in thickness. Excessive thickening may indicate endometrial hyperplasia, inflammation, or endometrial cancer. A diagnostic curettage with pathological examination is recommended. If malignancy is confirmed, total hysterectomy with bilateral salpingo-oophorectomy should be considered.

3. Menstrual Phase

This phase occurs during days 1–4 of the menstrual cycle. During this time, levels of estrogen and progesterone in the body gradually decrease, leading to shedding of the endometrial lining due to insufficient hormonal support. As a result, the endometrium is in an incomplete state, making it impossible to accurately assess its thickness.

In addition, in postmenopausal women, the normal endometrial thickness is usually less than 5 mm. Individuals experiencing abnormal endometrial thickness should promptly seek evaluation and treatment at a hospital gynecology department.