The endometrium is thickest during the secretory phase of the menstrual cycle and is usually about 10 to 12 mm thick. The endometrium changes with the menstrual cycle, which is divided into the proliferative phase, secretory phase and menstrual phase.
1. Proliferative phase: the proliferative phase is on the 5th~14th day of the menstrual cycle. In this phase, under the action of estrogen, the epithelium, glands, mesenchyme, and blood vessels on the surface of the endometrium show proliferative changes, and the thickness of the endometrium proliferates from about 3~5mm to about 8~10mm.
2. Secretory phase: the secretory phase is on the 15th to 28th day of the menstrual cycle. Under the action of estrogen and progesterone secreted by the corpus luteum, the endometrium in the proliferative phase becomes thicker and thicker, and the thickness of the endometrium in the secretory phase is around 10~12mm.
3. Menstrual period: the menstrual period is on the 1st~4th day of the menstrual cycle, at this stage, estrogen and progesterone retreat together, the endometrium sheds, and the thickness of the endometrium changes from about 10~12mm to about 3~5mm.
If you notice any thickening of the endometrium accompanied by heavy menstrual flow and prolonged menstrual period, you should consult a doctor promptly.