Biology · Chemical Coordination and Integration · NEET
The ovary is the primary female sex organ and also acts as an endocrine gland. It makes two groups of steroid hormones: estrogen, secreted mainly by the growing ovarian follicles, and progesterone, secreted mainly by the corpus luteum. Memory hook: follicle before ovulation makes Estrogen; the corpus luteum after ovulation makes Progesterone (P for Pregnancy).
Before ovulation the growing follicle secretes estrogen; after ovulation the corpus luteum secretes progesterone. Both are steroid hormones of the ovary.
Your doubts, answered
Does the follicle or the corpus luteum secrete estrogen?
The growing ovarian follicles secrete estrogen. NCERT states: estrogen is synthesised and secreted mainly by the growing ovarian follicles (before ovulation). After ovulation the ruptured follicle becomes the corpus luteum, which then secretes mainly progesterone. So estrogen = follicle phase, progesterone = corpus luteum phase.
What is the exact function of estrogen?
Estrogen does four NCERT-listed jobs: (1) stimulates growth and activity of female secondary sex organs, (2) develops the growing ovarian follicles, (3) causes the appearance of female secondary sex characters (like high pitch of voice), and (4) mammary gland development. It also regulates female sexual behaviour.
What does progesterone do?
Progesterone supports pregnancy. It also acts on the mammary glands and stimulates the formation of alveoli (sac-like structures that store milk) and milk secretion. In NEET matching questions, progesterone is paired with 'stimulates formation of alveoli in mammary glands'.
Are estrogen and progesterone peptide or steroid hormones?
Both are steroid hormones. NCERT lists estradiol (estrogen) and progesterone together with cortisol and testosterone under steroids. This is a common trap: glucagon and insulin are peptides, but ovarian hormones are steroids made from cholesterol.
Is the corpus luteum a permanent gland?
No. The corpus luteum is a temporary endocrine gland. It forms from the ruptured follicle after ovulation, secretes mainly progesterone, and then degenerates if pregnancy does not occur. NEET has directly asked 'a temporary endocrine gland in the human body' with the answer corpus luteum.
⚠️ The NEET trap ✗ Progesterone is secreted by the growing ovarian follicle. ✓ Progesterone is secreted mainly by the corpus luteum (formed after ovulation). The growing follicle secretes estrogen. 🧠 NTA loves swapping the source. Fix the timeline: follicle (before ovulation) = Estrogen; corpus luteum (after ovulation) = Progesterone. In the 2025 matching PYQ, Progesterone-Corpus luteum and Relaxin-Ovary were both keyed.
Real NEET questions
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 ruptured ovarian follicle is converted into the corpus luteum, which secretes mainly progesterone. It functions only temporarily during the cycle/pregnancy and then degenerates, so it is a temporary endocrine gland. The pineal gland is permanent; corpora cardiaca and allata are insect structures.
2016
Osteoporosis, an age-related disease of skeletal system, may occur due to
A · Immune disorder affecting neuromuscular junction leading to fatigue
B · High concentration of Ca++ and Na+
C · Decreased level of estrogen ✓
D · Accumulation of uric acid leading to inflammation of joints
Solution: Osteoporosis (loss of bone mass) commonly occurs in aged women after menopause due to a fall in estrogen. Estrogen, the chief ovarian follicular hormone, helps maintain bone integrity, so its decline weakens the skeleton.
2025
Match List-I with List-II. A. Progesterone B. Relaxin C. Melanocyte stimulating hormone D. Catecholamines / I. Pars intermedia II. Ovary III. Adrenal Medulla IV. Corpus luteum
A · A-II, B-IV, C-I, D-III
B · A-III, B-II, C-IV, D-I
C · A-IV, B-II, C-I, D-III ✓
D · A-IV, B-II, C-III, D-I
Solution: Progesterone is secreted mainly by the corpus luteum (A-IV); relaxin is produced by the ovary (B-II); MSH is secreted by the pars intermedia (C-I); catecholamines come from the adrenal medulla (D-III). This gives A-IV, B-II, C-I, D-III.
Solved Chemical Coordination and Integration NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The ovary secretes two groups of steroid hormones: estrogen (mainly from growing ovarian follicles) and progesterone (mainly from the corpus luteum).
Which ovarian hormone maintains pregnancy?
Progesterone supports pregnancy. It is secreted mainly by the corpus luteum and also stimulates alveoli formation and milk secretion in the mammary glands.
Why is estrogen linked to osteoporosis?
A decreased level of estrogen after menopause is a common cause of osteoporosis, because estrogen helps maintain bone mass. This is a repeated NEET fact (2016, 2018).
Is the ovary an exocrine or endocrine gland?
The ovary is both: it releases the ovum (a non-hormonal product) and it acts as an endocrine gland by secreting estrogen and progesterone directly into the blood.
Which cells or structure secretes estrogen in the ovary?
Estrogen is synthesised and secreted mainly by the growing ovarian follicles, before ovulation occurs.
