What does follicular phase mean?

The follicular phase refers to the period from the first day of a woman's menstruation to the day of ovulation, when the body is stimulated and affected by the follicles. The concentration of estrogen hormone in the woman's tongue begins to gradually increase, the follicles begin to mature, and the woman's endometrium thickens. The follicular phase is also called the ovarian cycle and is a normal phenomenon of the female body.

What does the follicular phase mean?

The follicular phase is from the first day of menstruation to the day of ovulation. During this period, under the influence of follicle-stimulating hormone, the concentration of estrogen in the body increases, the follicles gradually mature, and the endometrium thickens. The follicular phase, ovulatory phase, luteal phase and menstrual phase are the four different stages of the menstrual cycle, which is also called the "ovarian cycle."

Calculated every 28 or 30 days, the hormone levels and endometrial thickness in each stage change as follows: Follicular phase (5th-14th day of menstrual cycle): From the 5th day of menstruation, a new batch of follicles (10-15 candidates) in the ovaries begin to grow, and the primary follicles are selected, which can be seen by B-ultrasound around the 9th day. Estrogen levels rise significantly during this phase. The endometrium begins to grow from 1-2mm on the 6th day of menstruation to 8-10mm before ovulation. Ovulation period (one of the 14th, 15th, and 16th days of the menstrual cycle): The egg breaks out of the dominant follicle and estrogen reaches its peak.

There is a brief drop in estrogen when the egg is released (which is why there is a small amount of bleeding during ovulation). The endometrium should be 9-12mm during ovulation. Luteal phase (day 15-29 of the menstrual cycle): The ovulatory follicle forms a corpus luteum, which secretes a large amount of progesterone and estrogen. Progesterone reaches its peak on the 22nd to 23rd day. This is the most reliable time to measure progesterone levels and evaluate corpus luteum function.

The endometrium continues to thicken and is 15-19mm before menstruation. Menstrual period (1-5 days of menstrual cycle): corpus luteum atrophy, estrogen and progesterone decrease, and endometrial withdrawal bleeding. Because of this, some detailed examinations related to gynecological endocrinology are very particular about time: "6 items of sex hormones" require blood drawing on the 3rd day of menstruation; vaginal B monitoring of ovulation should start on the 9th day of menstruation, and then be done once before and after ovulation (while measuring the thickness of the endometrium). Follicle-stimulating hormone 40U/L, estradiol as low as 39nmol/ml or less, endometrium less than 5mm