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gonadotropic hormone

gonadotropic hormone (gō´nădətrŏp´Ĭk) or gonadotropin, any one of three glycoprotein (see protein) hormones released by either the anterior pituitary gland or the placenta (the organ in which maternal and fetal blood exchange nutrients and waste products) that have various effects upon the ovaries and testes (see testis). Gonadotropin-releasing hormone (Gn-RH) is produced and released from the hypothalamus. Gn-RH release stimulates the secretion of both follicle-stimulating hormone (FSH) and lutenizing hormone (LH) from the pituitary gland. Gn-RH is a peptide composed of ten amino acids which are synthesized in the hypothalamus (that portion of the brain nearest the pituitary). This hormone travels in the bloodstream to the anterior pituitary, where it causes the release of the gonadotropic hormones. The hormones FSH and LH inhibit the amount of Gn-RH released by a mechanism called "negative feedback." In the female, FSH causes an increase in the weight of the ovaries and encourages the growth of Graafian follicles (containing maturing eggs); in males, FSH produces spermatogenesis in the testes. In females, secretion of LH is associated with the maturation of the follicles, the manifestation of heat (or estrus), and the release of the egg from the follicle, which is transformed into a corpus luteum. In males, LH stimulates the testes to release testosterone. Sex hormones released from the ovaries and testes eventually reach the hypothalamus and help to regulate the hormonal cycle. Human chorionic gonadotropin (HCG), produced in the placenta, helps to maintain pregnancy once a fetus begins to develop. It appears in the urine in approximately the first week after the first missed menstrual period, and is the basis for two kinds of pregnancy tests; in the Ascheim-Zondek testm it causes the ovaries of an immature female rat or mouse to gain weight and produce ripened follicles, and in the Friedman test, it stimulates female rabbits to ovulate.

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gonadotropic hormone

go·nad·o·trop·ic hor·mone / gōˌnadəˈträpik; -ˈtrōpik/ (chiefly Brit. also gonadotrophic hormone / -ˈträfik; -ˈtrōfik/ ) • n. another term for gonadotropin.

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"gonadotropic hormone." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 24 Sep. 2018 <http://www.encyclopedia.com>.

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human chorionic gonadotropin

human chorionic gonadotropin (HCG): see gonadotropic hormone.

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Human Chorionic Gonadotropin

Human Chorionic Gonadotropin

Human chorionic gonadotropin (HCG) is a gly-coprotein hormone produced by the extraembryonic tissue of the early human embryo. After fertilization, the human zygote undergoes cleavage followed by the formation of a blastocyst. The blastocyst is a hollow sphere constructed of an inner cellmass, which becomes the embryo proper, and a trophoblast, which is embryonic tissue that will contribute to the formation of the placenta. The portion of the trophoblast that is invasive into the maternal uterus is known as the syncytiotrophoblast. The syncytiotrophoblast is the tissue of origin of HCG. The hormone is produced early in pregnancy and increases in rate of production until about the tenth week of pregnancy. Thereafter it decreases.

The function of HCG is to stimulate the production of progesterone by the corpus luteum. This assures a continual supply of ovarian progesterone until the placenta develops a supply of progesterone around seven weeks of gestation. Progesterone prepares the uterine lining, the endometrium, for implantation and maintainence of the embryo.

The presence of HCG in a womans urine indicates pregnancy by revealing the presence of trophoblast cellsalthough it does not in any way indicate the health of the fetus. Earlier, mouse (Aschheim-Zondek) and rabbit (Friedman) tests indicated the presence of HCG in urine. However, these were expensive. Later, the leopard frog, Rana pipiens, was shown to be much less expensive as a biological test organism. A male leopard frog will release living sperm in an hour after receiving an injection of morning urine containing HCG. Somewhat similarly, female African clawed frogs, Xenopus laevis, will release eggs after receiving an injection of HCG-containing urine. These tests have now been replaced with even more sensitive clinical tests, one of which will reveal pregnancy prior to the first missed period.

Cryptorchidism is a condition in which the testes do not descende into the scrotum of a newborn baby boy. This is a serious condition because abdominal testes are vulnerable to testicular cancer at a much higher incidence than normal testes. Further, abdominal testes are generally sterile. Some infants respond to HCG treatment of this condition. HCG enhances maturation of the external genitals and often causes the undescended testes to move into the scrotum.

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Human Chorionic Gonadotropin

Human chorionic gonadotropin

Human chorionic gonadotropin (HCG) is a glyco-protein hormone produced by the extraembryonic tissue of the early human embryo. After fertilization , the human zygote undergoes cleavage followed by the formation of a blastocyst. The blastocyst is a hollow sphere constructed of an inner cell mass , which becomes the embryo proper, and a trophoblast, which is embryonic tissue that will contribute to the formation of the placenta. The portion of the trophoblast that is invasive into the maternal uterus is known as the syncytiotrophoblast. The syncytiotrophoblast is the tissue of origin of HCG. The hormone is produced early in pregnancy and increases in rate of production until about the tenth week of pregnancy. Thereafter it decreases. The function of HCG is to stimulate the production of progesterone by the corpus luteum. This assures a continual supply of ovarian progesterone until the placenta develops a supply of progesterone around seven weeks of gestation. Progesterone prepares the uterine lining, the endometrium, for implantation and maintainence of the embryo.

The presence of HCG in the urine of a woman is indicative of pregnancy. Actually, the test reveals the presence of trophoblast cells and does not in any way indicate the health of the fetus. Early on, there were mice (Aschheim-Zondek) and rabbit (Friedman) tests for the presence of HCG in urine. However, these were expensive. Later, the leopard frog, Rana pipiens, was shown to be much less expensive as a biological test organism . A male leopard frog will release living sperm in an hour after receiving an injection of morning urine containing HCG. Somewhat similarly, female African clawed toads , Xenopus laevis, will release eggs after receiving an injection of HCG-containing urine. These tests have now been replaced with even more sensitive clinical tests, one of which will reveal pregnancy prior to the first missed period.

Cryptorchidism is a condition where the testes do not descent into the scrotum of a newborn baby. This is a serious condition because abdominal testes are vulnerable to testicular cancer at a much higher incidence than normal testes. Further, abdominal testes are generally sterile. Some infants respond to HCG treatment of this condition. HCG enhances maturation of the external genitals and often causes the undescended testes to move into the scrotum.

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"Human Chorionic Gonadotropin." The Gale Encyclopedia of Science. . Retrieved September 24, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/human-chorionic-gonadotropin-0

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