Luteal Regression And Menstruation

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F. Luteal Regression and Menstruation

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When no pregnancy occurs

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the CL will regress around 10 days post-ovulation-termed luteolysis

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(Figure 10). When pregnancy occurs

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the CL is maintained

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CL regression consists of two phases

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the control mechanisms of which are complex and differ

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between species.

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i.

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Functional luteolysis: may be a result of either low LH or high estrogen or both.

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i.

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Structural luteolysis: in humans may involve apoptosis

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although autophagocytosis has

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also been proposed to be the main mechanism involved in this process.

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Withdrawal of the ovarian steroids progesterone and estrogen:

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occurs with the onset of luteal regression. The CL physically decreases in size and is ultimately

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replaced by connective tissue. As a result of the whitish connective tissue

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the CL is now called

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the corpus albicans (Latin = ‘whitish body’).

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stimulates the release of PGF2-a

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which causes vasospasms of the spiral arteries and

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contractions of the myometrium (menstrual cramps).

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disrupts the blood supply to the endometrium that leads to hypoxia and tissue necrosis. The

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functionalis layer of the endometrium is thus sloughed off and expelled from the uterus by the

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uterine contractions

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leaving behind the basalis layer of the endometrium. The basalis will be the

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tissue foundation for the secretory endometrium of the next menstrual cycle.

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removes steroidal negative feedback on the pituitary. The pituitary gonadotropin output will

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therefore increase

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and a new menstrual cycle will ensue.