The hormone responsible for the production of breast milk:

IGNOU PB Bsc Entrance-2022

Obstetrics & Gynaecology

Easy

Appeared in: IGNOU PB Bsc Entrance-2022

Explanation

Prolactin is the principal hormone responsible for lactogenesis, which is the process of producing milk.
It is secreted by the anterior pituitary gland, and its levels rise significantly during pregnancy.
However, the milk-producing effect of prolactin is inhibited by high levels of progesterone and estrogen during pregnancy.
After delivery, the abrupt drop in progesterone and estrogen allows prolactin to stimulate the mammary alveoli to synthesize and secrete milk.

Option A: Human placental lactogen (hPL), also known as human chorionic somatomammotropin, primarily functions to alter maternal metabolism to support fetal growth. While it has weak lactogenic properties, it is not the main hormone responsible for milk production.
Option B: Oxytocin's role is in milk ejection (the 'let-down' reflex), not milk production. It stimulates the contraction of myoepithelial cells surrounding the breast alveoli, pushing the already-produced milk into the ducts so the infant can access it.
Option D: Progesterone, along with estrogen, actively inhibits milk production during pregnancy by blocking the action of prolactin on the breast tissue. Lactation is initiated only after progesterone levels fall dramatically following the delivery of the placenta.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal Regulation of Lactation as background academic context rather than a clinical decision trigger.
Understanding the difference between prolactin and oxytocin is fundamental for troubleshooting breastfeeding issues. Low milk supply may relate to prolactin issues, while difficulty with let-down points to oxytocin.
Lactational amenorrhea, the temporary cessation of menstruation, is caused by high prolactin levels which suppress gonadotropin-releasing hormone (GnRH), thus inhibiting ovulation. This provides a natural, though not foolproof, form of contraception.
Certain medications, like some antipsychotics (e.g., risperidone) or antihypertensives (e.g., methyldopa), can increase prolactin levels and cause galactorrhea (inappropriate milk production).

How to Approach the Question

First, identify the key action word in the question: 'production'. This is the central clue.
Differentiate this from other related actions, such as milk 'ejection' or 'let-down'.
Recall the primary roles of the hormones listed in the context of pregnancy and lactation.
Associate Prolactin with 'Production' (P for P).
Associate Oxytocin with 'ejection' or 'let-down'.
Remember that Progesterone and Estrogen are high during pregnancy and inhibit milk production.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 3 p. 69-71

E6 Physiology Essentials Sembulingam 10e Part 2 p. 150-152

E6 Obstetrics Williams p. 48-68