Corpus Luteum: Formation and Progesterone Function
Biology · Human Reproduction · NEET
After ovulation, the empty part of the ruptured Graafian follicle changes into a yellow body called the corpus luteum. It secretes large amounts of progesterone, which keeps the endometrium (uterus lining) thick and ready for the embryo. Memory hook: "Corpus luteum = the follicle's leftover shell that becomes a Progesterone factory." This is a NEET favourite because it links ovulation, the luteal phase and pregnancy in one structure.
The ruptured Graafian follicle becomes the corpus luteum, which secretes progesterone to maintain the endometrium. With fertilisation, hCG keeps it working; without fertilisation it degenerates, causing menstruation.
Your doubts, answered
Corpus luteum is formed from which structure?
It is formed from the remaining parts of the ruptured Graafian follicle after ovulation. Once the ovum is released, the empty follicle does not disappear. Its cells enlarge and transform into the corpus luteum (Latin for 'yellow body'). So the same follicle that released the egg becomes the corpus luteum.
What hormone does the corpus luteum secrete?
The corpus luteum secretes large amounts of progesterone. NCERT states it 'secretes large amounts of progesterone which is essential for maintenance of the endometrium.' It also secretes some estrogen and, during later pregnancy, relaxin. But for NEET the key answer is progesterone.
What is the function of progesterone from the corpus luteum?
Progesterone keeps the endometrium thick and rich in blood vessels and glands. This maintained endometrium is needed for implantation of the fertilised ovum and for the events of pregnancy. Progesterone also suppresses FSH and LH, so no new follicle grows during the luteal phase.
Why does the corpus luteum degenerate?
If fertilisation does NOT happen, the corpus luteum degenerates on its own. Its progesterone support to the endometrium stops, so the endometrium disintegrates. This breakdown of the endometrial lining is what causes menstruation and starts a new cycle. If fertilisation occurs, hCG from the embryo keeps the corpus luteum alive.
Is the corpus luteum a temporary or permanent endocrine gland?
It is a temporary endocrine gland. It forms only after ovulation and lasts a short time, then degenerates if pregnancy does not occur. This exact point was asked in NEET 2017: 'A temporary endocrine gland in the human body is' — answer, corpus luteum.
What is the difference between corpus luteum and corpus albicans?
Corpus luteum is the active yellow body that secretes progesterone. When it degenerates (no pregnancy), it turns into a white scar tissue called corpus albicans, which is inactive. Corpus luteum = working; corpus albicans = dead remnant. NCERT names corpus luteum; corpus albicans is the degenerated form.
Does the corpus luteum belong to the follicular or luteal phase?
The luteal phase. Ovulation ends the follicular phase; the phase after it is the luteal phase, named after the corpus luteum. NEET 2018 matched Secretory Phase with Luteal Phase because progesterone from the corpus luteum makes the endometrium secretory.
⚠️ The NEET trap ✗ The corpus luteum secretes mainly estrogen (like the growing Graafian follicle). ✓ The corpus luteum secretes mainly PROGESTERONE. The growing follicle secretes estrogen; after ovulation the leftover follicle becomes the corpus luteum and switches to progesterone. 🧠 Before ovulation = follicle = estrogen. After ovulation = corpus luteum = progesterone. NEET ReNEET 2026 marked a statement wrong for saying the corpus luteum secretes estrogen.
Real NEET questions
NEET 2017
A temporary endocrine gland in the human body is
A · Pineal gland
B · Corpus cardiacum
C · Corpus luteum ✓
D · Corpus allatum
Solution: After ovulation the remnant of the Graafian follicle becomes the corpus luteum, which secretes progesterone but exists only for a short time before it degenerates if there is no fertilisation. This makes it a temporary endocrine gland. The pineal gland is permanent; corpus cardiacum and corpus allatum are insect endocrine structures.
NEET 2019 (Odisha)
No new follicles develop in the luteal phase of the menstrual cycle because
A · Follicles do not remain in the ovary after ovulation
B · FSH levels are high in the luteal phase
C · LH levels are high in the luteal phase
D · Both FSH and LH levels are low in the luteal phase ✓
Solution: In the luteal phase the corpus luteum secretes large amounts of progesterone, which suppresses the release of gonadotropins. So both FSH and LH stay low. Because FSH (which drives follicular growth) is low, no new follicle can develop during this phase.
NEET 2023
Assertion A: Endometrium is necessary for implantation of blastocyst. Reason R: In the absence of fertilization, the corpus luteum degenerates that causes disintegration of endometrium.
A · Both A and R are true and R is the correct explanation of A
B · Both A and R are true but R is NOT the correct explanation of A ✓
C · A is true but R is false
D · A is false but R is true
Solution: A is true: the endometrium must be thick for the blastocyst to implant. R is also true: without fertilisation the corpus luteum degenerates, so progesterone falls and the endometrium disintegrates (menstruation). But R explains why the endometrium breaks down, not why it is needed for implantation, so R is NOT the correct explanation of A.
Solved Human Reproduction NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is Latin for 'yellow body'. The structure looks yellowish because of fat and pigment in its cells. It forms from the ruptured Graafian follicle after ovulation.
When is the corpus luteum most active?
During the luteal phase, roughly day 15 to day 28 of a 28-day cycle. It peaks in progesterone secretion about a week after ovulation, preparing the endometrium for a possible pregnancy.
What keeps the corpus luteum alive if pregnancy occurs?
The hormone hCG (human chorionic gonadotropin), secreted by the developing embryo/placenta. hCG maintains the corpus luteum so it keeps making progesterone to support early pregnancy.
Does the corpus luteum secrete relaxin?
Yes. During the later phase of pregnancy the ovary (corpus luteum) secretes relaxin, which helps relax the pelvic ligaments. NEET 2021 asked this and the answer was corpus luteum.
Which phase and hormone does NEET link with the corpus luteum?
Luteal phase (also called secretory phase) and progesterone. Progesterone makes the endometrium secretory and maintains it for implantation.
