Which of the following hormones is responsible for the milk let-down reflex during lactation?

Raj. CHO - 2023

Obstetrics & Gynaecology

Easy

Appeared in: Raj. CHO - 2023

Explanation

Oxytocin, released from the posterior pituitary gland, is the primary hormone responsible for the milk let-down (ejection) reflex.
It is released in response to nerve signals sent from the nipple to the hypothalamus when an infant suckles.
Oxytocin acts on the myoepithelial cells surrounding the mammary alveoli, causing them to contract and squeeze milk into the ducts, making it available to the infant.
This process is a classic example of a neuroendocrine reflex, where a nervous system stimulus leads to a hormonal response.

Option B: Prolactin is responsible for milk synthesis (production), not its ejection. It stimulates the glandular cells in the alveoli to produce milk.
Option C: Estrogen's main role is in the development of the breast's ductal system during pregnancy. High levels of estrogen (and progesterone) actually inhibit milk secretion before birth.
Option D: Growth hormone plays a permissive or supportive role in the development of breast tissue, but it is not the direct trigger for the acute milk let-down reflex.

Visual 1: Diagram - A flowchart illustrating the neuroendocrine pathway of the milk let-down reflex. It should show: 1. Infant suckling (stimulus). 2. Nerve pathway to the hypothalamus. 3. Signal to the posterior pituitary. 4. Release of oxytocin into the blood. 5. Oxytocin acting on myoepithelial cells in the breast. 6. Milk ejection.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of lactation, specifically the milk let-down reflex as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in educating new mothers about the let-down reflex, explaining that it can take 30-60 seconds to start and may be accompanied by a tingling sensation.
Nursing interventions to promote the let-down reflex include ensuring a comfortable and calm environment, encouraging skin-to-skin contact, teaching correct latching techniques, and suggesting warm compresses.
What if? If a mother is experiencing significant stress, pain, or anxiety, the release of oxytocin can be inhibited, preventing the let-down reflex. Nursing care should focus on identifying and mitigating these factors through pain management, relaxation techniques, and emotional support to facilitate successful breastfeeding.

How to Approach the Question

Identify the key physiological process in the question: 'milk let-down reflex'. This term specifically refers to the ejection or release of milk.
Differentiate this process from 'milk production' or 'milk synthesis', which are related but distinct functions in lactation.
Recall the primary hormones involved in lactation. A key mnemonic is: Prolactin = Production; Oxytocin = Out (ejection).
Evaluate the options based on this distinction. Prolactin is the main distractor as it's also crucial for lactation, but for production, not ejection.
Select Oxytocin as the hormone directly responsible for the muscular contraction that causes the 'let-down' or ejection of milk.

Concept Tested & Keywords

Concept Tested: Hormonal regulation of lactation, specifically the milk let-down reflex.
Stem keywords: hormones, milk let-down reflex, lactation
Lead-in keywords: Which

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