# Ovarian Cycle and Folliculogenesis

> Ovarian cycle and folliculogenesis for NEET-PG Obstetrics and Gynaecology, covering follicle recruitment, dominance, ovulation and corpus luteum function.

- Canonical URL: https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/ovarian-cycle-and-folliculogenesis
- Exam / course: NEET-PG · Subject: Obstetrics and Gynaecology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: Williams Gynecology; Guyton and Hall Textbook of Medical Physiology
- How to cite: "Ovarian Cycle and Folliculogenesis", PrepElephant, https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/ovarian-cycle-and-folliculogenesis

## Direct answer

Folliculogenesis is the growth of an oocyte-containing follicle from the primordial stage to the preovulatory antral stage, and the ovarian cycle is the monthly cycle of follicle development, ovulation and corpus luteum formation. Each cycle begins with FSH recruiting a cohort of antral follicles, of which one becomes dominant and ovulates in response to the LH surge. The ovarian cycle is therefore driven by gonadotropins, but its outputs, oestradiol and progesterone, feed back on the pituitary and hypothalamus to shape the next cycle.

## What you must remember

- **Primordial follicles:** formed in fetal life and held in arrest; the reserve is established before birth and declines steadily through life.
- **Stages:** primordial, primary, secondary, antral and preovulatory (Graafian), with granulosa layers multiplying and the antrum forming in the antral stage.
- **Recruitment:** FSH rescues a cohort of antral follicles from atresia in the early follicular phase, which is the key step that makes a cycle possible.
- **Dominance:** the dominant follicle is selected by its FSH sensitivity and high aromatase activity, and it suppresses its rivals by producing oestradiol.
- **Ovulation:** the LH surge, triggered by sustained high oestradiol through positive feedback, leads to ovulation about 24 to 36 hours after the surge begins.
- **Corpus luteum:** the luteinised follicle secretes progesterone and oestradiol under LH, lasts about 14 days, and regresses unless pregnancy rescues it through hCG.
- **Two-cell two-gonadotropin theory:** theca cells under LH make androgens, and granulosa cells under FSH convert them to oestradiol through aromatase.

## A worked cycle from day one to ovulation

Picture a 28-year-old with a 28-day cycle, and follow the ovary through each stage.

1. **Recruit a cohort.** On day one, falling progesterone and oestradiol allow FSH to rise slightly, and a cohort of small antral follicles is recruited under its influence.
2. **Compete for FSH.** Through the early follicular phase, granulosa cells proliferate and begin to express aromatase, and the follicles compete for FSH.
3. **Select the dominant follicle.** By about day seven or eight, the leading follicle has more FSH receptors and keeps growing when its rivals are starved of FSH, so it becomes dominant.
4. **Trigger the LH surge.** The dominant follicle produces rising oestradiol, which first suppresses FSH and then, once it is high and sustained, triggers the LH surge through positive feedback at the hypothalamus and pituitary.
5. **Ovulate and form the corpus luteum.** The LH surge matures the dominant follicle, reinitiates meiosis in the oocyte and causes ovulation roughly a day after the surge begins. The collapsed follicle becomes the corpus luteum, which secretes progesterone under LH, so the endometrium moves into the secretory phase.
6. **Regress or rescue.** If pregnancy does not occur, the corpus luteum regresses after about 14 days, oestradiol and progesterone fall, and the next cohort is recruited.

This pathway explains why the luteal phase is relatively fixed at about 14 days while the follicular phase varies.

## Where the exam tries to catch you

The hormone, cell and timing traps recur in almost every ovarian cycle question.

- **Trap:** confusing the roles of LH and FSH in the two-cell theory. — **Correct:** theca cells express LH receptors and make androgens, whereas granulosa cells express FSH receptors and convert androgen to oestradiol through aromatase.
- **Trap:** placing ovulation at the peak of the LH surge. — **Correct:** ovulation follows the surge by about a day, not at its peak, so read a stem's day of ovulation in that light.
- **Trap:** treating the luteal phase as variable. — **Correct:** it is generally fixed at about 14 days, and it is the follicular phase that changes between women.
- **Trap:** equating the primordial reserve with the cycle's output. — **Correct:** only one follicle usually ovulates per cycle, far fewer than the reserve.

## Frequently asked questions

### Which gonadotropin recruits the cohort of antral follicles each cycle?

FSH recruits the cohort of antral follicles in the early follicular phase by rescuing them from atresia. Without this FSH support, the follicles would regress and no dominant follicle would form.

### Why does the LH surge cause ovulation?

The LH surge is triggered by sustained high oestradiol from the dominant follicle through positive feedback at the hypothalamus and pituitary. The surge matures the follicle, restarts meiosis in the oocyte and leads to ovulation about a day later.

### What does the two-cell two-gonadotropin theory describe?

The two-cell two-gonadotropin theory describes how theca cells under LH make androgens and granulosa cells under FSH convert those androgens into oestradiol through aromatase. Both gonadotropins are needed to produce oestradiol in the ovary.

### How long does the corpus luteum last in a non-pregnant cycle?

The corpus luteum lasts about 14 days in a non-pregnant cycle, after which it regresses and oestradiol and progesterone fall. If pregnancy occurs, hCG from the trophoblast rescues the corpus luteum and keeps it functioning.