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Hormones secreted by the Placenta (when pregnant)

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Progesterone. For the synthetic progestogens with effects similar to progesterone, see Progestin.


Progesterone (pregn-4-ene-3,20-dione; abbreviated as P4) is an endogenous steroid hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species.[1] It belongs to a group of steroid hormones called the progestogens,[1] and is the major progestogen in the body. Progesterone is also a crucial metabolic intermediate in the production other endogenous steroids, including the sex hormones and the corticosteroids, and plays an important role in brain function as a neurosteroid.[2] Chemistry[edit] Progesterone was independently discovered by four research groups.[3][4][5][6] Willard Myron Allen co-discovered progesterone with his anatomy professor George Washington Corner at the University of Rochester Medical School in 1933. Like other steroids, progesterone consists of four interconnected cyclic hydrocarbons.

Estriol. Estriol (also oestriol or E3) is one of the three main estrogens produced by the human body.


Biosynthesis[edit] Human steroidogenesis, showing estriol at bottom right. In essence, it follows the pathway from dehydroepiandrosterone or DHEA (at left), but with a modified DHEA with an additional OH-group. Estriol is only produced in significant amounts during pregnancy as it is made by the placenta from 16-hydroxydehydroepiandrosterone sulfate (16-OH DHEAS),[1] an androgen steroid made in the fetal liver and adrenal glands. The human placenta produces pregnenolone and progesterone from circulating cholesterol. Levels[edit] Levels of estriol in non-pregnant women do not change much after menopause, and levels are not significantly different from levels in men.

Therapeutic use[edit] In pregnant women with multiple sclerosis, estriol reduces the disease's symptoms noticeably,[2] according to researchers at UCLA's Geffen Medical School. Human chorionic gonadotropin. In molecular biology, human chorionic gonadotropin (hCG) is a hormone produced by the syncytiotrophoblast, a portion of the placenta following implantation.[1][2] The presence of hCG is detected in pregnancy tests.

Human chorionic gonadotropin

Some cancerous tumors produce this hormone; therefore, elevated levels measured when the patient is not pregnant can lead to a cancer diagnosis. However, it is not known whether this production is a contributing cause or an effect of tumorigenesis. The pituitary analog of hCG, known as luteinizing hormone (LH), is produced in the pituitary gland of males and females of all ages.[1][3] As of December 6, 2011[update], the United States FDA has prohibited the sale of "homeopathic" and over-the-counter hCG diet products and declared them fraudulent and illegal.[4][5][6] Human placental lactogen. Human placental lactogen (hPL), also called human chorionic somatomammotropin (HCS), is a polypeptide placental hormone.

Human placental lactogen

Its structure and function is similar to that of human growth hormone. It modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus. hPL has anti-insulin properties. hPL is a hormone secreted by the syncytiotrophoblast during pregnancy. Like human growth hormone, hPL is encoded by genes on chromosome 17q22-24. It was identified in 1963.[2] Structure[edit] hPL molecular mass is 22,125 and contains single chain consisting of 191 amino acid residues that are linked by two disulfide bonds and the structure contains 8 helices.

Levels[edit] hPL is present only during pregnancy, with maternal serum levels rising in relation to the growth of the fetus and placenta. Activin and inhibin. Not to be confused with the agent that was referred to as 'inhibine' prior to its identification as hydrogen peroxide.

Activin and inhibin

Activin and inhibin are two closely related protein complexes that have almost directly opposite biological effects. Identified in 1986,[1][2] activin enhances FSH biosynthesis and secretion, and participates in the regulation of the menstrual cycle. Many other functions have been found to be exerted by activin, including roles in cell proliferation, differentiation, apoptosis,[3] metabolism, homeostasis, immune response, wound repair,[4] and endocrine function.

Conversely inhibin downregulates FSH synthesis and inhibits FSH secretion.[5] Activin is a dimer composed of two identical or very similar beta subunits. Structure[edit] In mammals, four beta subunits have been described, called activin βA, activin βB, activin βC and activin βE. The βC subunit is able to form activin heterodimers with βA or βB subunits but is unable to dimerize with inhibin α.[12]