What kills a corpus luteum? - (May/01/2008 )

Hello,

High school bio teacher, trying to plug some holes here...

All the texts we have state that after ovulation, the corpus luteum forms and does its hormonal thing
for roughly two weeks, then it 'decays' or 'disintegrates' unless it is rescued by human chorionic
gonadotropin from an implanted zygote.

What I'm wondering is - what is the 'clock' on the corpus luteum? What is it that runs
out around day 14 and causes the CL to stop working, and what change is caused by
hCG that allows the CL to continue firing for several extra months?

(Bonus question - around 10-12 weeks the placenta starts producing its own estrogen
and progesterone, making the CL superfluous...does it die then? If so, why?)

I am no expert, but I would guess it is the female hormone cycles that govern this. Certain precise, balanced levels of reproductive hormones may be trigeering proliferation and cell death, which would lead to formation and end of corpora lutea. And the hormonal clocks are well established in literature.

Anyway, look up first result powerpoint seminar here.. I am too lazy to open it, but the title sounds promising:)
http://search.vadlo.com/b/q?sn=158621799&a...uteum&rel=2

Gonadotropin loss is the signal for CL degneration

Paper explaining it all here

Apparently the CL can persist up to the second trimester during pregnancy, but usually degenerates before this.