Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: DrN on 03/01/2005 21:27:14
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I've been wondering this for a while, and can't seem to find out for myself - when you take the contraceptive pill eggs are prevented from being released from the ovaries, hence preventing fertilisation. but what happens to all these unreleased eggs? are they reabsorbed or do they just sit there waiting, like they have done since birth?
Does this mean that if you've been on the pill for 15 years, you have 15 years worth of extra eggs?
If the eggs go through enough of the maturation cycle before they would normally be released, could the non-release contribute to polycystic ovary syndrome (PCOS)?
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It depends what sort of pill you take. The progresterone-only pill (minipill) works by thickening cervical mucus and rendering the endometrium (lining of the uterus) unreceptive for implantation. You can still ovulate on the minipill I believe.
But the combined pill (containing oestrogen and progesterone) works by inhibiting ovulation. Oral intake of the hormones raises blood oestrogen and progesterone levels which feedback negatively to the hypothalamus in the brain, switching off the production of the peptide hormones which trigger ovulation. There is an article by Sarah Urquhart on the site which explains this in slightly more detail :
http://www.thenakedscientists.com/HTML/articles/article/sarahurquhartcolumn1.htm
But whether pill use abolishes totally the maturation of any follicles, or whether the ovary just becomes quiescent whilst on the pill, I'm not sure. It's a good question.
I'll ask around because, to my knowledge, women who have used the combined pill enter menopause at the same age as women who haven't. If pill users were putting their ovaries into a state of virtual 'suspended animation' one would anticipate that they would have more eggs in reserve and hence they should menstruate for longer (i.e. reach menopause later).
Sit tight and I'll find out.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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thanks for that, I'll take a look at the link. I'll have to continue my research on the internet - if I discover anything before you do I'll post it!
i can't remember when the combined pill came into common use - presumably the first 'batch' of users would be well into menopause by now? I suppose you'd have to be on it for quite a number of years for any potential difference outside of the normal range (which is huge!) to be identified.
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Okay, I've had a chat with my colleague who is a gynaecologist.
He agrees that combined oral contraceptives do not delay menopause and hence the follicles in the ovary, whilst not maturing to eggs, nonetheless continue to be 'consumed' by the ovary, despite suppression of ovulation. Therefore the eggs must be being recruited but then undergoing spontaneous involution (apoptosis) prior to maturation. How this is achieved is not clear.
My suggestion is that just as in a normal menstrual cycle when 40 or so eggs initially begin to develop and eventually involute leaving just 1 dominant follicle to ovulate, perhaps the oestrogen in the pill simulates that dominant follicle, causing those eggs that switch on at the start of the month to kill themselves.
Anyway, problem cleared up !
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Great! thanks, all sorted in my mind now.
L