The final effect of hCG (human chorionic gonadotropin) is to maintain the corpus luteum, which, in turn, produces estrogen and progesterone, ultimately thickening the uterine lining and suppressing menstruation to support a developing pregnancy.
Here's a more detailed breakdown:
hCG plays a crucial role in early pregnancy. After fertilization and implantation, the developing embryo begins to secrete hCG. This hormone acts primarily to:
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Sustain the Corpus Luteum: The corpus luteum is a temporary endocrine gland in the ovary that produces estrogen and progesterone. hCG prevents its breakdown, ensuring continued hormone production.
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Stimulate Estrogen and Progesterone Production: The corpus luteum, under the influence of hCG, continues to secrete estrogen and progesterone. These hormones are vital for preparing and maintaining the uterine lining (endometrium).
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Thicken the Uterine Lining: Estrogen and progesterone work together to thicken and enrich the endometrium, making it a suitable environment for the developing embryo. This thickened lining provides nutrients and support.
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Suppress Menstruation: High levels of estrogen and progesterone suppress the release of gonadotropin-releasing hormone (GnRH), which in turn inhibits the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). This hormonal cascade prevents the maturation and release of new eggs and stops menstruation. Effectively, the body receives a signal that it is pregnant and should not shed the uterine lining.
In essence, hCG ensures that the hormonal environment remains favorable for the embryo's implantation and initial development until the placenta takes over the production of estrogen and progesterone. The placenta eventually produces sufficient estrogen and progesterone on its own, making the corpus luteum less critical.
