CLC - Certified Lactation Counselor Physiology of Lactation Questions and Answers — Questions and Answers
Question 1: A new mother reports that she feels a tingling sensation in her breasts shortly after her baby begins to nurse, and sometimes when she hears her baby cry. Which hormone is primarily responsible for this sensation, known as the milk ejection reflex or 'let-down'?
- Prolactin
- Estrogen
- Oxytocin (Correct answer)
- Progesterone
Correct answer: Oxytocin
Oxytocin is the hormone responsible for the milk ejection reflex, or 'let-down'. It causes the myoepithelial cells surrounding the alveoli in the breast to contract, squeezing milk into the ducts. This reflex can be triggered by the baby suckling, or by psychological stimuli like hearing the baby cry or thinking about the baby.
Question 2: A client who is 4 days postpartum is concerned because her breasts have suddenly become very full, firm, and tender. She states she was only producing small amounts of yellowish milk (colostrum) before this. This sudden increase in milk volume marks the transition into which stage of lactation?
- Lactogenesis I
- Lactogenesis II (Correct answer)
- Lactogenesis III (Galactopoiesis)
- Involution
Correct answer: Lactogenesis II
Lactogenesis II is the onset of copious milk secretion, often referred to as the milk 'coming in'. This stage typically occurs 2-5 days postpartum and is triggered by the rapid drop in progesterone levels after the delivery of the placenta, while prolactin levels remain high.
Question 3: Which of the following is the primary hormonal stimulus for milk synthesis (production) within the alveolar cells of the breast?
- Oxytocin
- Human Placental Lactogen (hPL)
- Progesterone
- Prolactin (Correct answer)
Correct answer: Prolactin
Prolactin, secreted by the anterior pituitary gland, is the primary hormone responsible for stimulating the lactocytes (milk-producing cells) in the alveoli to synthesize milk. While high levels of progesterone during pregnancy inhibit prolactin's full effect, the drop in progesterone after birth allows prolactin to initiate copious milk production.
Question 4: A mother who exclusively breastfeeds her baby from only her right breast for several days notices that her left breast has significantly decreased in milk production, while the right breast continues to produce an ample supply. This localized control of milk synthesis is primarily regulated by:
- Systemic prolactin levels
- A feedback inhibitor of lactation (FIL) in the milk (Correct answer)
- The frequency of the oxytocin reflex
- Maternal hydration status
Correct answer: A feedback inhibitor of lactation (FIL) in the milk
The principle of supply and demand in lactation is managed locally within each breast by a small whey protein known as the Feedback Inhibitor of Lactation (FIL). When milk is not removed from the breast, FIL accumulates and signals the alveolar cells to slow down milk synthesis. Frequent and effective milk removal removes FIL, thus signaling the breast to produce more milk.
Question 5: During pregnancy, the breasts are prepared for lactation, and colostrum production begins (Lactogenesis I). However, copious milk production is inhibited until after birth. Which hormone is primarily responsible for preventing significant lactation during pregnancy?
- Prolactin
- Progesterone (Correct answer)
- Oxytocin
- Testosterone
Correct answer: Progesterone
High levels of progesterone, produced by the placenta during pregnancy, inhibit the action of prolactin on the alveolar cells, thus preventing copious milk secretion. The dramatic drop in progesterone levels after the placenta is delivered is the key trigger for Lactogenesis II, the onset of abundant milk production.
Question 6: A breastfeeding mother is experiencing significant emotional stress and anxiety. She reports that although her breasts feel full, her baby seems frustrated at the breast and is having difficulty getting the milk to flow. This difficulty is most likely due to the inhibition of which hormone by stress?
- Estrogen
- Prolactin
- Progesterone
- Oxytocin (Correct answer)
Correct answer: Oxytocin
The milk ejection reflex, which is controlled by oxytocin, can be inhibited by stress, pain, or anxiety. Even if the breasts are full of milk (due to prolactin activity), high levels of stress hormones can interfere with the release of oxytocin from the posterior pituitary, preventing the myoepithelial cells from contracting and ejecting the milk.
CLC - Certified Lactation Counselor Physiology of Lactation Questions and Answers
A new mother reports that she feels a tingling sensation in her breasts shortly after her baby begins to nurse, and sometimes when she hears her baby cry.
Which hormone is primarily responsible for this sensation, known as the milk ejection reflex or 'let-down'?