After two weeks, the ovulated egg remains unfertilized, and the corpus luteum stops producing progesterone and breaks down.
Human chorionic gonadotropin (hCG). It is the hormone secreted by the placenta in pregnant women.
Human chorionic gonadotropin is a hormone produced by cells that surround the growing human embryo; These cells eventually go on to form the placenta.
Human chorionic gonadotropin can be detected in the urine 7 to 9 days after fertilization as the embryo attaches and implants in the uterus. A doctor can request this hormone test or carry it out without medical requirements.
During the menstrual cycle, when an egg is released from the ovary at ovulation, the remnants of the ovarian follicle (which surrounds the egg) form a new temporary ovarian gland called the corpus luteum, which produces the hormone progesterone.
A feedback mechanism signals the pituitary gland to produce follicle-stimulating hormone (and, to a lesser extent, luteinizing hormone) to start the next menstrual cycle.
However, suppose the ovulated egg is fertilized by sperm, and an embryo is created. The corpus luteum must continue to produce progesterone until the placenta is established (the placenta takes over progesterone production).
The corpus luteum must continue to produce progesterone because the loss of progesterone leads to the loss of the uterus lining (menstruation), which would prevent an embryo from implanting.
Human chorionic gonadotropin is the embryonic hormone that ensures that the corpus luteum continues to produce progesterone during the first trimester of pregnancy.
In addition to maintaining progesterone production from the ovary, human chorionic gonadotropin may also ensure that the lining of the uterus (endometrium) is ready to receive the implanted embryo.
Recent studies have indicated that human chorionic gonadotropin may help increase the blood supply to the uterus and participate in the remodeling of the lining of the uterus in preparation for the implanted embryo.
- Promotion of progesterone production from the corpus luteum.
- Angiogenesis of the uterine vasculature.
- Cytotrophoblast differentiation.
- Immunosuppression and blocking of invading trophoblastic cell phagocytosis.
- The growth of the uterus is in line with fetal growth.
- The inactivity of uterine muscle contraction.
- Promotion of growth and differentiation of fetal organs.
- Growth and development of the umbilical cord.
- Endometrial blastocyst signals before implantation.
HCG in sperm and receptors found in the fallopian tubes, suggesting pre-pregnancy communication
The hCG receptors in the brain hippocampus, hypothalamus, and brainstem can cause nausea and vomiting during pregnancy.
How is human chorionic gonadotropin controlled?
Human chorionic gonadotropin is produced by trophoblast cells surrounding the developing embryo at approximately five days of pregnancy.
The amount of human chorionic gonadotropin in the bloodstream doubles every 2-3 days as the development of the embryo and placenta continues and levels peak around six weeks of pregnancy.
After this peak, human chorionic gonadotropin levels decline (although they remain detectable during pregnancy).
Once the placenta is established, it becomes the primary source of progesterone production (around week 12 of pregnancy), and human chorionic gonadotropin is no longer needed to maintain ovarian function.
However, human chorionic gonadotropin may have additional beneficial effects in the later stages of pregnancy; researchers are currently investigating such roles.
Maternal blood levels
Levels peak at 8 to 10 weeks of pregnancy, then decrease and are lower throughout the remainder of the pregnancy.
- 0-1 week: 0-50 mIU / ml.
- 1-2 weeks: 40-300 mIU / ml.
- 3-4 weeks: 500-6,000 mIU / ml.
- 1-2 months: 5,000-200,000 mIU / ml.
- 2-3 months: 10,000-100,000 mIU / ml.
- 2do trimestre: 3,000-50,000 mIU / ml.
- 3rd trimester: 1,000-50,000 mIU / ml.
Non-pregnant women: <5.0 mIU / ml Postmenopausal women: <9.5 mIU / ml.
What happens if I have excess human chorionic gonadotropin?
There is no substantial evidence that high levels of human chorionic gonadotropin cause direct negative consequences.
Very high levels of human chorionic gonadotropin are rare. Still, they may indicate hyperproliferation of the placenta (also known as hydatidiform moles or molar pregnancies), which in some cases can lead to cancer (choriocarcinomas).
Human chorionic gonadotropin levels can also be elevated in association with cancers unrelated to pregnancy (e.g., kidney, breast, lung, and gastrointestinal tract). In such cases, human chorionic gonadotropin levels in the blood/urine can serve as a tumor marker.
In pregnancy, a link between elevated human chorionic gonadotropin levels and Down syndrome development has also been suggested.
Studies have shown that human chorionic gonadotropin levels in a Down syndrome pregnancy are approximately twice that of an unaffected pregnancy.
However, high levels of human chorionic gonadotropin do not cause Down syndrome (instead, it is caused by an extra chromosome at position 21).