Question
Which of the following statements about prolactin is correct?
| A. |
Prolactin initiates ovulation
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| B. |
Prolactin causes milk ejection during suckling
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| C. |
Prolactin inhibits the growth of breast tissue
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| D. |
Prolactin secretion is tonically inhibited by the hypothalamus
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Show Answer
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Correct Answer » D
Explanation
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|
- The hypothalamus continuously suppresses prolactin secretion via dopamine (Prolactin Inhibitory Factor).
- This is unique among anterior pituitary hormones because:
- Most are under stimulatory control, but prolactin is under inhibitory control.
- When dopamine inhibition is reduced (e.g., suckling, dopamine antagonists), prolactin levels rise.
Explanation of Incorrect Options
A. Prolactin initiates ovulation
- Prolactin actually inhibits ovulation.
- Mechanism:
- Suppresses GnRH (Gonadotropin-Releasing Hormone) → ↓ LH & FSH
- Clinical correlation:
- Hyperprolactinemia → amenorrhea, infertility
B. Prolactin causes milk ejection during suckling
- Milk ejection (let-down reflex) is mediated by oxytocin, not prolactin.
- Prolactin → milk production
- Oxytocin → milk ejection
C. Prolactin inhibits the growth of breast tissue
- Prolactin promotes breast development and lactation, not inhibition.
