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-   -   prolactin and oxytocin query!! (https://www.usmle-forums.com/usmle-step-1-forum/3264-prolactin-oxytocin-query.html)

doctorF 07-13-2010 02:48 AM

prolactin and oxytocin query!!
 
" After labor, a precipitous ↓ in estrogen and progesterone relieves the down-regulation of the prolactin receptor → prolactin induces lactation."


i read this in one of the banks... guys is this correct???? is it not that the prolactin causes milk production and oxytocin causes ejection??? plz xplain

lee-usmle 07-13-2010 05:59 AM

Yes, correct
 
Yes, that's true.

During pregnancy the high level of estrogen stimulates prolactin secretion from the anterior pituitary. This increased prolactin causes growth of mammary tissue in preparation for lactation.

However, at the same time the high level of estrogen and progesterone during pregnancy blocks the "milk receptors" of prolactin so that milk production does not happen during pregnancy.

After birth and removal of the placenta and the decrease in estrogen and prolactin there will be no more down regulation of these prolactin receptors and milk production can start but this time it has to be stimulated by baby suckling. If no suckling milk production stops.

Oxytocin is also stimulated by baby suckling and it aids in milk let down (ejection) not milk production.

Sabio 07-13-2010 09:22 PM

Estogen blocks prolactin, Progesterone does not
 
That's why estrogen should not be given for lactating mothers as a form of contraception. You can give only progesterone and you can begin progesterone immediately after birth because it does not block the prolactin receptors.




Seetal 07-14-2010 01:15 AM

yes also in third class teaching hospitals, the pregnant ladies' nipples are stimulated (like as if a baby is sucking) to induce a milk-let down-like reaction so that oxytocin is released n this oxytocin will help with the uterus contraction to ease delivery.

Androide89 07-14-2010 02:10 AM

Quote:

Originally Posted by Sabio (Post 11889)
That's why estrogen should not be given for lactating mothers as a form of contraception. You can give only progesterone and you can begin progesterone immediately after birth because it does not block the prolactin receptors.

In kaplan physio notes page 474 2007 version, it says estrogens AND progesterone block milk synthesis?

Also, FA correction: FA p482 - Pregnancy - Lactation is induced by a "decrease in maternal progesterone" in the presence of high prolactin levels rather than a "decrease in maternal steroids."


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