Endometrial hyperplasia

With endometrial hyperplasia, endometrial refers to the endometrium, which is the inner lining of the uterus, and hyperplasia means increased growth, so endometrial hyperplasia means excessive growth of the inner lining of the uterus.

The uterus consists of 3 layers, an outer thin layer called the perimetrium or the serosa, a middle smooth muscle layer called the myometrium, and the innermost layer, the endometrium.

The endometrium has two layers, an inner functional layer made up mainly of glands and supporting connective tissue, called stroma, and an outer thin basal layer which regenerates the overlying functional layer after each menstrual cycle.

Now, the growth of the functional layer is regulated by the hormones secreted by the ovaries. Each ovary is made up of a number of ovarian follicles.

Each follicle consists of an oocyte, which is the female germ cell, surrounded by an outer layer made up of theca cells, which secrete androgens, also known as the male hormones, and an inner layer made up of granulosa cells, which secrete estrogen.

Now estrogen stimulates the growth of endometrial glands and stroma.

This effect of estrogen predominates during the first phase of the menstrual cycle.

This is also called the proliferative phase because it’s when the lining of the endometrium grows.

At the end of this phase, ovulation occurs, where one ovarian follicle expels the oocyte into the fallopian tube and it travels to the uterus.

During the second phase of the menstrual cycle, also called the secretory phase, the remaining structure of the follicle, now called the luteal body, begins to secrete progesterone.

Progesterone counteracts the effect of estrogen on the endometrium by stopping its growth.

At the same time, it causes the glands to produce secretions that acts as nutrients for any developing embryo.

Endometrial hyperplasia most often results when the endometrium is exposed to high levels of estrogen for a prolonged time.

This leads to excessive growth of endometrial glands relative to stroma; meaning a high gland-to-stroma ratio.