Placental Hormones Flashcards by joseph dizon

Human Chorionic Gonadotropin

Act via

Plasma membrane LH-HCG receptor

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Human Chorionic Gonadotropin

After 5 weeks of gestation it is produce by

Syncytiotrophoblast

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Human Chorionic Gonadotropin

Beta HcG is also produced in the

Fetal kidney

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Human Chorionic Gonadotropin

Also secreted by trophoblastic neoplasm and use as

Tumor marker

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Human Chorionic Gonadotropin

Found in very small amount in tissue of

Men and non pregnant woman

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Human Chorionic Gonadotropin

Release HCG less than 5 weeks

Cytotrophoblast and

Syncytiotrophoblast

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Human Chorionic Gonadotropin

> 8 weeks release by

Syncytiotrophoblast

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Human Chorionic Gonadotropin

Plasma half life of

36 hours

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Human Chorionic Gonadotropin

Composed of alpha ____ and beta ____ sub units

Alpha 92

Beta 145

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Human Chorionic Gonadotropin

Alpha sub unit is structurally identical with

LH
FSH
TSH is related to H-mole

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Human Chorionic Gonadotropin

Single gene is located at

Chromosome 6

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Human Chorionic Gonadotropin

Of the 7 genes

6 genes for beta HCG

1 gene for beta Lh

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Human Chorionic Gonadotropin

Both sub units are synthesized and cleaved by

Endopeptidases

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Human Chorionic Gonadotropin

Assembled and rapidly released by

Excocytosis of secretory granules

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Site of HCG synthesis

HCG mRNA for both alpha and beta subunits are greater than at

Term pregnancy

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Molecular form of HCG in plasma and urine

Free alpha subunits increase gradually and steadily until they plateau at

36 weeks

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Molecular form of HCG in plasma and urine

Complete beta HCG molecule is maximal at

8-10 weeks

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Concentration of HCG in serum and urine

Intact HCG is detectable in plasma of pregnant women

7-9 days after the mid cycle surge of LH that preceded ovulation

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Concentration of HCG in serum and urine

HCG enters maternal blood at the time of

Blastocyst implantation

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Concentration of HCG in serum and urine

Evidence of HCG levels doubles within

48-72 hours

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Concentration of HCG in serum and urine

Peak maternal plasma levels between

69-80 days of menses

2-3 months of LMP

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Concentration of HCG in serum and urine

Begins to decline at

10-12 weeks and undetectable in the serum by 16 weeks AOG

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Concentration of HCG in serum and urine

Principal urinary form is the

Beta core fragment

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Higher maternal plasma HCG levels

Multi fetal pregnancy
Erythroblastosis fetalis
Fetal hemolytic anemia
Gestational trophoblastic disease
Down syndrome
Syphilis
Big placenta

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Lower HCG plasma levels

Early pregnancy | Ectopic pregnancy

Renal clearance of HCG accounts for

30 percent of its metabolic clearance, | Remainder is likely cleared by metabolism in the liver

Clearance of beta and alpha subunit are about

10 | 30 fold

Both HCG subunits are required for binding to the

LH HCG receptor in the corpus luteum and the fetal testis

Most important function of HCG is

Maintenance of function of corpus luteum (progesterone production ) in early pregnancy

HCG acts an LH surrogate to stimulate replication og

Leydig cells and testosterone synthesis | To promote male sexual differentiation

HCG promotes what? To promote uterine vascular vasodilatation and myometrial muscle relaxation.

Remain secretion

Human placental lactogen Prolactin like activity secreted by

Anterior pituitary gland

Human placental lactogen Immuno chemical resemblance to

Human growth hormone

Human placental lactogen Detected as early as

2nd to 3rd week of fertilization

Human placental lactogen Demonstrated in _________ before 6 weeks

Cytotrophoblast

Human placental lactogen Chemical structures

191 AA residues | Structurally similar to human prolactin

Human placental lactogen Located at

Chromosome 17

Human placental lactogen Assess after 6 weeks postpartum for gestational diabetes

Increase concentration during pregnancy and post partum

Human placental lactogen Detected in placenta within

5-10 days after conception

Human placental lactogen Detected in maternal serum as early as

3 weeks

Human placental lactogen Maternal plasma concentration are linked to placental mass and rises steadily until

34-36 weeks

Human placental lactogen Half life

Between 10-30 minutes

Human placental lactogen In the first half of pregnancy leads to an increase in hpl plasma concentration

Prolonged maternal starvation

Human placental lactogen Stimulated by

Insulin | Insulin like growth factor

Human placental lactogen Inhibited by

PGE2 andPGE2 alpha

Normally secreted by adipocytes

Leptin

Leptin Synthesized by

Cytotrophoblast | Syncytiotrophoblast

Leptin Inhibit

Apoptosis and promotes trophoblastic proliferation

Leptin Function

Anti obesity | Regulate bone growth and immune function leptin

Neuropeptide Y Localized in

Cytotrophoblast

Neuro peptide Y Causes

CRH release

Inhibin Acts to inhibit

Pituitary FSH release

Inhibin Produced by

Human testis Ovarian granulosa cells - corpus luteum and trophoblast

Inhibin Maternal serum levels peak at

Term

Inhibin Inhibit

FSH secretion | Ovulation during pregnancy

Inhibin Act via GnRH to regulate placental

HCG synthesis

Expressed in the placental and amnion No detectable in fetal blood before labor but is present in umbilical cord blood after labor begins Declines rapidly after delivery

Activin

Progesterone

Corpus luteum

Progesterone > 8 weeks AOG produced by

Placenta

Progesterone Normal production rate in pregnancy women

250 mg

Progesterone In multi fetal pregnancies it may exceed

600 mg/ day

Progesterone Placental progesterone production

Cholesterol converted to Pregnenolone within mitochondria catalyzed by Cytochrome p450

Progesterone After canalizations by cytochrome p450. It is then converted to

Progesterone in endoplasmic reticulum by | 3 beta hydroxysteroid dehydrogenase

Progesterone Released through the process of

Diffusion

Progesterone Placenta relies on

Exogenous cholesterol for progesterone production

Progesterone Principal precursor

Cholesterol maternal

Progesterone Uses LDl cholesterol for progesterone biosynthesis

Trophoblast

Estrogens relies principally on

Fetal adrenal precursor

Progesterone During pregnancy there is an increase in plasma concentration of

5 alpha dihydroprogesterone

Progesterone Also converted to

Potent mineralocorticoid deoxycorticosterone in pregnant and in fetus

Primary hormone during proliferative phase

Estrogen

Estrogen First 2-4 weeks of pregnancy rising HCG levels maintain production of

Estradiol in maternal corpus luteum

Estrogen Decrease significantly at

7 weeks | Lutheal phase transition

Estrogen Most potent estrogen in the system

Estradiol

Estrogen Estradiol production within the corpus luteum of non pregnant as well as early pregnancy

Luthenized theca | Granulosa cells

Estrogen Not expressed in human placenta - conversion of C21 to C19 steroid is impossible

Steroid 17 alpha hydroxylase

Estrogen Obligatory precursor of estrogen

C19 steroid

Estrogen Placenta gas a high capacity to convert C19 to

Estrone and estradiol

Estrogen Acted upon by 3beta-hydroxysteroid dehydrogenase type 1 to produce androstenedione

DHEA

Estrogen Converts androstenedione to estrone which is converted to 17 beta hydroxysteroid dehydrogenase type 1

Cytochrome p450 aromatase

Estrogen It is found that woman who had anencephalic fetuses has a

Very low estrogens level of about 10%

Estrogen Anencephalic fetus need

Folic acid | Vit B12

Estrogen Principal precursor for placental estradiol synthesis

DHEA-S

Estrogen Most important source of placental estrogen

Fetal adrenal glands

Estrogen To prevent neural tube defect how many folic acid

400 mg

Estrogen More than 90% of estradiol and estriol formed enters

Maternal plasma

Estrogen 85% or more of placental progesterone enters

Maternal plasma

Estrogen Steroids secreted from syncytiotrophoblast can enter maternal blood directly unlike when hormones enter

Blood

Human chorionic gonadotropin Biological activity similar to

luteinizing hormone