What Is Endometrial Hyperplasia?
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Endometrium is the lining of the womb (uterus), which is normally shed every month during the childbearing years, unless the woman conceives. Endometrial hyperplasia is overgrowth of the lining of the womb, beyond the normal 5 millimeters in thickness. It is also called endometrial hypertrophy. Hyperplasia can occur throughout the entire uterine lining, or may only affect an isolated area. Endometrial hyperplasia is not cancer, but it can cause cellular changes that predispose an affected woman to developing cancer later. Most endometrial hyperplasia develops from a hormonal imbalance, where there is a dominance of estrogen and a deficiency of progesterone.
Normal endometrium is one layer of epithelium, the tissue that lines organs, resting on a stroma, a mat of connective, supportive tissue. A fertile woman has a functional layer of endometrium next to her empty uterine cavity, and a basal layer riding over the muscle of her uterus, the myometrium (not shown on above diagram). Only the functional layer is shed during menstruation. If the woman does not conceive, myometrium contracts to expel the endometrium through the vagina as part of the normal menstrual flow. Myometrium also expels the fetus during childbirth. Normal epithelium is columnar, meaning its length is four times its width. Glands run from the top of the endometrium down into the stroma. Spiral arteries feed the endometrium with blood.
From Day 1 to Day 4 of a normal menstrual cycle, when you are bleeding, the endometrium is thin because the functional layer (epithelium) is absent. During the estrogen phase (first half of a normal cycle, from Day 4 to Day 14), the lining of your uterus proliferates or grows. Proliferative endometrium has tubular glands and columnar cells. Proliferative endometrium does not shed, but continues to build up unless the estrogen is opposed by progesterone. At mid-cycle, around Day 14, your ovary releases an egg for fertilization (ovulation) and produces progesterone. Progesterone is only produced once ovulation occurs. Progesterone makes the lining of your uterus hospitable for an embryo. During the progesterone phase (second of a normal cycle, from Day 15 to Day 28), your endometrium secretes and is thick. Secretory endometrium has winding (tortuous) glands with vacuoles or bubbles. If conception does not take place, only secretory endometrium sheds during menstruation.
Endometrium is the blood-rich tissue that nourishes the fertilized egg when it first implants in the uterus. If the woman conceives, the blood vessels and glands of the endometrium (decidua) fuse to become the placenta, which sustains her pregnancy. If a woman does not consistently release an egg at mid-cycle (anovulation) then there is a sustained absence of progesterone. The lining of her uterus may become abnormally thickened due to the dominance of estrogen and her periods will be very heavy (menorrhagia) and often painful (dysmenorrhea). An infertile woman may have no periods (amenorrhea) or infrequent periods (oligomenorrhea).
A menopausal woman who is taking estrogen replacement therapy and has not had a hysterectomy requires progesterone supplements to prevent the lining of her uterus from thickening and bleeding from resuming. Estrogen replacement therapy (ERT) alone can make your endometrium dangerously thick (hyperplastic) and prone to cancer.