So....which hormone ACTUALLY maintains the corpus luteum?

[September24]

I'm a bit confused on what hormones maintain the corpus luteum during the menstrual cycle.

I know that HCG is released by the trophoblasts to help maintain the corpus luteum which will keep secreting progesterone thus maintaining the uterine lining.

However, I have read that LH is very similar to HCG since they both maintain the corpus luteum. How does this work? LH in a way helps make estrogen so does estrogen help maintain the corpus luteum as well?

How exactly does LH maintain the corpus luteum? I always thought that LH just functions in the luteal surge and making estrogen.

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[Czarcasm]

I haven't studied this stuff in years (from my first MCAT), but I was curious so I looked it up. This is from my A&P Book:

Luteal phase: [..] The ovulated follice has now become a structure called the corpus luteum, named for a yellow lipid that accumulates in the theca interna cells. These cells are now called lutein cells. The transformation from ruptured follice to corpus luteum is regulated by LH; hence, LH is also called luteotropic hormone.

LH stimulates the corpus luteum to continue growing and to secrete rising levels of estradiol and progesterone. The most important aspect of the luteal phase is a 10-fold increase in progesterone level. This hormone has a crucial role in preparing the uterus for the possibility of pregnancy. Notwithstanding its luteinizing role, however, LH secretion declines steadily over the rest of the cycle, as does FSH. This is because the high levels of estradiol and progesterone, along with inhibin from the corpous luteum, having a negative feedback effect on the pituitary.

A few pages later (regarding hormones of pregnancy):
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Human chorionic gonadotropin (HCG) is secreted by the blastocyst and placenta. [...] HCG secretion peaks around 10 to 12 weeks and then falls to a relatively low level for the rest of gestation. Like LH, it stimulates growth of the corpus luteum, which doubles in size and secretes increasing amounts of progesterone and estrogen. Without HCG, the corpus luteum would atrophy and the uterus would expel the conceptus.

Estrogens: [..] The corpus luteum is an important source of estrogen for the first 12 weeks; after that, it comes mainly from the placenta. [..] Estrogen stimulates tissue growth in the fetus and mother.

I guess this doesn't really answer the why or how part of your question, but I suppose it has a positive effect on cell growth, whereas other hormones (that it suppresses) would cause those cells to atrophy and die.

 

[dyspareunia]

I'm a bit confused on what hormones maintain the corpus luteum during the menstrual cycle.

I know that HCG is released by the trophoblasts to help maintain the corpus luteum which will keep secreting progesterone thus maintaining the uterine lining.

However, I have read that LH is very similar to HCG since they both maintain the corpus luteum. How does this work? LH in a way helps make estrogen so does estrogen help maintain the corpus luteum as well?

How exactly does LH maintain the corpus luteum? I always thought that LH just functions in the luteal surge and making estrogen.

hCG maintains the corpus luteum. Forget about LH.