The endometrial stripe refers to the thickness of the endometrium, the inner lining of the uterus. This tissue prepares for a potential pregnancy each month.
It is typically visualized and measured using transvaginal ultrasound, appearing as a bright line in the center of the uterus. Its primary function is to thicken and create a nourishing environment for a fertilized egg. If pregnancy does not occur, the lining is shed during menstruation.
What is the Endometrial Stripe?
The endometrial stripe is the visualization of the endometrium, the lining of the uterus, on an ultrasound image. This tissue undergoes regular changes in thickness and appearance throughout a woman’s reproductive life.
Measurement is usually performed via transvaginal ultrasound, which provides a detailed view of the uterine lining. The appearance of the endometrial stripe varies predictably with hormonal changes, reflecting the different phases of the menstrual cycle.
Normal Thickness Ranges by Life Stage
The normal thickness of the endometrial stripe varies considerably depending on a woman’s life stage and hormonal status. There is no single universal normal value, as it changes with the menstrual cycle in pre-menopausal women and stabilizes after menopause.
For pre-menopausal women, the endometrial stripe’s thickness fluctuates throughout the menstrual cycle. During menstruation, it is at its thinnest, typically 2 to 4 millimeters. In the early proliferative phase (around days 6-14), the lining begins to thicken, usually measuring 5 to 7 millimeters.
As the cycle progresses into the late proliferative phase, the endometrium continues to grow, potentially reaching up to 11 millimeters before ovulation. During the secretory phase, after ovulation, the lining is at its thickest, typically 7 to 16 millimeters, as it prepares for possible embryo implantation.
In post-menopausal women not on hormone replacement therapy (HRT), the endometrial stripe generally remains thin, less than 5 millimeters. This thinning is due to the natural decline in estrogen levels after menopause, which no longer stimulates the monthly thickening and shedding of the uterine lining. If a post-menopausal woman experiences vaginal bleeding, an endometrial stripe greater than 4 mm may warrant further investigation.
For post-menopausal women using hormone replacement therapy, the endometrial stripe may be thicker than in those not on HRT. Thickness can vary, with some measurements around 8 mm, while others suggest an upper limit around 5 mm, or even over 8 mm in some cases.
Understanding Abnormal Thickness
An endometrial stripe thickness outside the expected normal ranges can indicate underlying conditions. Both a lining that is too thin (endometrial atrophy) and one that is too thick (endometrial hyperplasia) can be a medical concern, often relating to hormonal imbalances or other uterine pathologies.
Endometrial atrophy refers to a thinning of the uterine lining, commonly observed in post-menopausal women due to decreased estrogen levels. It can sometimes lead to post-menopausal bleeding and is generally non-cancerous.
Conversely, endometrial hyperplasia describes an abnormal thickening of the uterine lining, resulting from an excessive proliferation of endometrial cells. This condition is often linked to an imbalance of hormones, specifically too much estrogen without enough progesterone. Endometrial hyperplasia can cause abnormal uterine bleeding and, in some cases, may be a precursor to endometrial cancer.
Common Causes of Abnormal Thickness
Several conditions can lead to an abnormal endometrial stripe thickness. An increased thickness is frequently associated with an excess of estrogen not adequately balanced by progesterone.
Common causes of increased endometrial thickness include endometrial polyps, which are growths of endometrial tissue, and submucosal fibroids, benign growths that can protrude into the uterine cavity. Endometrial hyperplasia, an overgrowth of the uterine lining cells, is another frequent cause. Endometrial cancer itself is also a cause of increased thickness.
A decreased endometrial thickness, or thin endometrium, can also occur due to various factors. Low estrogen levels are a common cause, often seen in post-menopausal women or those with certain hormonal imbalances. Other reasons can include uterine scarring, such as from Asherman’s syndrome, which can result from previous uterine surgeries like dilation and curettage (D&C) or infections.
When is Endometrial Stripe Thickness Measured?
Measuring the endometrial stripe thickness is a routine part of gynecological assessments. It provides valuable information about the health and condition of the uterine lining, helping guide further diagnostic steps and management plans.
One common reason for measurement is to investigate abnormal uterine bleeding, particularly in post-menopausal women. Unexpected bleeding after menopause often prompts an ultrasound to evaluate the endometrial stripe, as a thickened lining can be a sign of hyperplasia or, less commonly, cancer.
The measurement is also performed during fertility work-ups, as an appropriately thick endometrial lining is necessary for successful embryo implantation. Doctors may monitor endometrial thickness in women undergoing assisted reproductive technologies to support pregnancy. It can also be part of evaluating symptoms like irregular periods or pelvic pain.