International Board of Certified Lactation Consultant (IBCLC) Practice Exam

What inhibits the continuous production of milk if the breasts are not frequently emptied?

1. Oxytocin

2. Prolactin

3. Feedback inhibitor of lactation (FIL)

4. Estrogen

The correct answer is: Feedback inhibitor of lactation (FIL)

The continuous production of milk is influenced by several hormonal factors, but specifically, the feedback inhibitor of lactation (FIL) plays a crucial role in milk production regulation. FIL is a protein produced in the milk itself. When the breasts are not emptied regularly, the concentration of FIL increases in the milk that remains in the breast. This high level of FIL sends signals to the lactating breast that inhibit further milk production. This feedback mechanism ensures that milk production aligns with the baby's feeding needs. If milk is not removed, either through breastfeeding or pumping, the increasing levels of FIL will lead to a decrease in the synthesis of milk. Essentially, the presence of FIL serves to prevent overproduction of milk that is not needed, thus maintaining a balance. Other hormonal influences, such as oxytocin and prolactin, while important in the lactation process, do not directly inhibit milk production in the same way FIL does. Oxytocin is involved in milk ejection during feeding, and prolactin is crucial for milk synthesis but does not regulate based on breast fullness. Estrogen plays a role in breast development and preparation for lactation but is not involved in the inhibition of milk production linked to the fullness of the breasts.