Difference Between Proliferative and Secretory Endometrium

The key difference between proliferative and secretory endometrium is that proliferative endometrium grows under the influence of estrogen while secretory endometrium grows under the influence of progesterone.

Proliferative and secretory endometrium are two changes in the endometrium during the menstrual cycle. In proliferative endometrium, the endometrium’s cells multiply and spread. During this change, the estrogen level rises, and the endometrium becomes thick. This phase lasts for 10-12 days. In the secretory endometrium, ovaries release a mature egg, and the next phase of menstruation begins. The new mature endometrium cells become ready for an egg to be implanted. If it does not happen, the body discards the endometrial lining. Progesterone is high in this phase. This stage lasts for usually another 13-14 days period.

CONTENTS

1. Overview and Key Difference
2. What is Proliferative Endometrium
3. What is Secretory Endometrium
4. Similarities Between Proliferative and Secretory Endometrium
5. Side by Side Comparison – Proliferative vs Secretory Endometrium in Tabular Form
6. Summary

What is Proliferative Endometrium?

During the menstrual cycle, the endometrium grows under the influence of estrogen. This stage of endometrium in the menstrual cycle is called proliferative endometrium. This is also called the follicular phase. Proliferative endometrium is a common, non-cancerous change that develops in the inner lining of the uterus. It is a normal feature in women of reproductive age. In the first part of the menstrual cycle, between menses and ovulation, the endometrium grows under the influence of estrogen.

These changes occur in the fertile age. It starts in the early teens and lasts at the age between 45-55. The diagnosis of a disordered proliferative endometrium is usually made after a small sample of tissue is removed from the endometrium through a procedure called endometrial biopsy or uterine curetting. This stage extends for about 10-12 days, usually from day 6 to 13 in a 28 days cycle. Furthermore, in this phase, the primary follicle changes to the Graafian follicle. The endometrium is about 2-3 mm thick. Most importantly, uterine glands do not secrete watery secretion.

What is Secretory Endometrium?

After ovulation, the endometrium grows under the influence of progesterone. This is known as secretory endometrium. Secretory endometrium is a normal non-cancerous change seen in the tissue that lies inside of the uterus of women. This is also a normal feature in women of reproductive age. During this phase, the endometrial glands become long and twisted. It secretes watery secretions. Hence, pathologists are calling this a secretory endometrium.

The menstrual flow might occur every 21 to 35 days and usually lasts two to seven days. The diagnosis of secretory endometrium is usually made after a small sample of tissue is removed from the endometrium. This procedure is known as endometrial biopsy. In this phase, the empty Graafian follicle changes into the corpus luteum. Furthermore, progesterone is high in this stage. The thickness of the endometrium is usually 5mm, and the uterine glands secrete watery secretion as well.  This stage extends for 13-14 days after ovulation (usually from day 15 to 28 in a 28 days cycle).

What are the Similarities Between Proliferative and Secretory Endometrium?

• Both are connected to the menstrual cycle.
• They are different phases of the endometrium during the menstrual cycle.
• Both are non-cancerous normal changes occurring in the tissue inside the uterus.
• They are normal findings in women of reproductive age.

What is the Difference Between Proliferative and Secretory Endometrium?

Proliferative endometrium is the endometrium that grows under the influence of estrogen, and in this phase, uterine glands do not secrete watery secretion. Secretory endometrium is the endometrium that grows under the influence of progesterone, and in this phase, uterine glands secrete a watery secretion. So, this is the key difference between proliferative and secretory endometrium.

Furthermore, in proliferative endometrium, the primary follicle changes to the Graafian follicle and the endometrium is about 2-3 mm thick. In contrast, in secretory endometrium, the empty Graafian follicle changes into corpus luteum and the thickness of the endometrium is usually 5 mm. Thus, it is also an important difference between proliferative and secretory endometrium. Moreover, in the proliferative endometrium, the uterine glands do not secrete watery secretion. On the other hand, in the secretory endometrium, the uterine glands secrete a watery secretion.

The below infographic presents the differences between proliferative and secretory endometrium in tabular form.

Summary – Proliferative vs Secretory Endometrium

The endometrial tissue is a sensitive target for steroid sex hormones and is able to change its structural characteristics. The endometrium is the innermost part of the uterus. Its structure and thickness vary throughout the menstrual cycle. During the menstrual cycle, estrogen influences the growth of the proliferative endometrium. After ovulation, progesterone influences the growth of the secretory endometrium. Thus, this is the key difference between proliferative and secretory endometrium.

Reference:

1. “Proliferative Endometrium.” MyPathologyReport.ca, 4 Jan. 2021, Available here.
2. “Secretory Endometrium.” MyPathologyReport.ca, 4 Jan. 2021, Available here.

Image Courtesy:

1. “Proliferative endometrium – very high mag.” By Nephron – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Secretory phase endometrium — low mag” By Nephron – Own work (CC BY-SA 3.0) via Commons Wikimedia