Lactation and Its Hormones
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Direct answer
Milk production and milk ejection are two different hormonal events, and separating them answers most questions on lactation. During pregnancy, estrogen and progesterone, supported by placental lactogen, drive the mammary glands to full development; after delivery, prolactin from the anterior pituitary initiates and maintains milk synthesis in the alveoli. Oxytocin from the posterior pituitary then performs the second act — contracting the myoepithelial cells around the alveoli so stored milk is ejected into the ducts, the let-down reflex, triggered by the baby's suckling. The first milk, colostrum, is a yellowish antibody-rich secretion that gives the newborn its earliest passive immunity.
What you must remember
- Division of labour: prolactin makes milk; oxytocin delivers it — a pairing NCERT states and every coaching test recycles in some costume.
- Development phase: estrogen and progesterone from the ovary and placenta, with placental lactogen, grow the ducts and alveoli during pregnancy; lactation proper begins towards the end of pregnancy.
- Colostrum: the milk of the first few days, containing several antibodies absolutely essential for the newborn's resistance, per NCERT — commonly identified as IgA in wider reading.
- Suckling reflex: nipple stimulation sends neural signals to the hypothalamus, which orders release of both oxytocin (immediate ejection) and prolactin (synthesis for the next feed) — a neuroendocrine loop.
- Posterior pituitary origin: oxytocin is synthesised in hypothalamic neurons and only stored and released by the posterior pituitary.
- Oxytocin's second job: the same hormone strengthens uterine contractions during labour, linking the reproductive chapter's two feedback stories.
- Breast-feeding endorsement: NCERT calls breast-feeding beneficial for the infant's health and immunity, aligning with India's promotion of early and exclusive breastfeeding under national health programmes.
Follow the reflex from the baby's mouth to the alveolus
Begin with the infant's first suckle. Sensory nerves in the nipple carry the message to the hypothalamus, which does two things at once. Neurons releasing oxytocin fire into the posterior pituitary, and within seconds the hormone reaches the breast, squeezing myoepithelial cells so milk squirts into the ducts — the mother literally feels the let-down, sometimes at the mere cry of her baby, which shows how conditioned the loop is. Simultaneously, prolactin-releasing signals to the anterior pituitary raise prolactin so the alveoli manufacture milk for the next feed. Production matches demand: frequent suckling keeps prolactin high, and weaning, by removing the stimulus, winds the gland down.
Colostrum deserves its own sentence in any answer. It is thicker and yellower than mature milk, richer in protein and antibodies, and mildly laxative in helping the newborn pass meconium, per standard texts. NCERT's examinable point is simpler and firmer: the first milk contains several antibodies essential for resistance in newborns — the baby's immune system is naive, and this passive transfer covers the gap until its own antibodies appear.
Where students lose marks
The prolactin-oxytocin swap is the chapter's most reliable error: a stem saying "hormone responsible for milk ejection" wants oxytocin, while "milk production" wants prolactin, and both appear together among the options precisely to harvest confusion. Second, oxytocin's origin: writing "secreted by posterior pituitary" is acceptable shorthand, but a strictly-worded question about synthesis expects the hypothalamus. Third, colostrum questions: its defining NCERT feature is antibody content, not fat or vitamin content, so choose the immunity option when in doubt. Finally, do not credit the placenta with lactation hormones after delivery — the placenta is gone, and its lactogen with it.
Frequently asked questions
Which hormone produces milk in the mammary glands?
Prolactin from the anterior pituitary initiates and maintains milk synthesis.
Which hormone causes milk ejection and how?
Oxytocin from the posterior pituitary contracts myoepithelial cells around the alveoli, forcing milk into the ducts.
What is colostrum and why is it important?
The first milk secreted during the initial days after birth, rich in antibodies essential for the newborn's resistance to infection.
How does suckling increase milk secretion?
Suckling stimulates the hypothalamus, raising prolactin release for continued synthesis and oxytocin release for ejection.
Which hormones prepare the breasts during pregnancy?
Ovarian and placental estrogen and progesterone, supported by placental lactogen, develop the ducts and alveoli.