Topic 6

Chorionic meaning

To do with the placenta

Are hormonal units of foetus & mother integrated/separate

Fetal, placental & maternal compartments form an integrated hormonal unit → feto-placental-maternal (FPM) unit → creates the Endocrine Environment

Role of the Endocrine Environment

Maintains and drives the processes of pregnancy and pre-natal development

What type of protein is Human Chorionic Gonadotrophin

Glycoprotein

Human Chorionic Gonadotrophin molecular weight

30,000

Human Chorionic Gonadotrophin is produced by what cells

Trophoblastic Cells

Human Chorionic Gonadotrophin subunits

α Subunit = Common with FSH, TSH, LH

β subunit = Hormone Specific

When does Human Chorionic Gonadotrophin begin to be excreted

Implantation

How many days after fertilisation can Human Chorionic Gonadotrophin be detected in blood

8 days

How many days after fertilisation can Human Chorionic Gonadotrophin (HCG) be detected in urine

14 days

When do HCG secretion levels peak

2 Months of Gestation

Role of hCG

Prevents Ovulation

↑ Endometrial Growth

Thyroid-stimulating

↑ Testosterone

Maintains the corpus luteum for 12 weeks

Makes sure uterine environment is receptive to pregnancy - angiogenesis, recruits Treg cells, inhibits dendritic cells)

Effect on immune system → changes function of T cells

How do pregnancy tests work

On the T line there’s an antibody to hCG

If there’s hCG present, it will bind to the antibody & cause the colour change

Human Chorionic Somatomammotrophin (hCS) molecular weight

38,000

Human Chorionic Somatomammotrophin (hCS) is similar to what other 2 hormones

Similar to Growth Hormone and Prolactin

They have a Common Progenitor

hCS is synthesised by what

Placenta

When is hCS secreted

Week 5 Post Fertilisation

Low levels of hCS indicate what? why?

Low levels indicative of placental insufficiency as its secretion is Directly Proportional To Placental Size

hCS (human chorionic somatomammotropin) is also known as what

hPL (human placental lactogen)

Effects of hCS (human chorionic somatomammotropin) on foetus & mother

Mother uses fat for energy more than glucose because foetus uses glucose

How do steroid levels in pregnancy compare with that of the menstrual cycle

Progesterone and Oestrogen Levels are higher

Sources of steroids throughout pregnancy

Corpus luteum in 1st trimester

Placenta starts taking over @ week 8 (luteal-placental shift)

Placenta is the main source by week 12

Why is the timing of the luteal-placental shift clinically important

Removal of the ovaries (with CL) before the luteal-placental shift leads to miscarriage

Pregnancy continues normally if the ovaries are removed after the luteal-placental shift

What form of oestrogen is highest in the menstrual cycle & what is highest in pregnancy

Menstrual cycle = estadiol

Pregnancy = estriol

Pregnenolone forms from what, where (fetus/placenta/mother)

Formed from cholesterol (from LDL) in all 3 - foetus, placenta, mother

Where can pregnenolone be converted to DHEA

Foetal adrenal gland & in the mother (not the placenta)

Where is DHEA converted to oestrogen

Placenta

Progesterone is formed from what

Maternal Precursors

Do levels of progesterone vary much throughout pregnancy

Levels Increase Significantly Throughout Pregnancy

80-90% of progesterone is produced by what and sent where

By the placenta

Sent to both foetus & mother

Role of progesterone in mother

Decreases Uterine Contractility (so drop in progesterone indicates pregnancy coming to an end)

Inhibits Ovulation - Acting on GnRH, FSH and LH

Maintain Uterine Function - Placental Secretion and Function

Embryo Nutrition - Increases Decidual Cells & Uterine Secretion

Role of progesterone in embryo

Precursor for other Hormones:

• Adrenal Hormones - Weak Androgen (Oestrogen)

• Cortisol - Surfactant Production

• Testicular Hormones - Testosterone (Foetal Differentiation)

What forms of oestrogen are present in pregnancy

Oestrone, Oestriol, 17b-Oestradiol

Is oestriol a strong/weak oestrogen

weak

Does oestrogen in pregnancy have a maternal/foetal/placental origin

All 3 (Placental Produced Oestrogens Transfer to Maternal and Foetal Compartments)

What do oestrogens form from

C-19 Steroids in the Adrenal Glands are converted into Weak Androgens (Dehydroepiandrostenedione (DHEA), 17-OH -DHEA) which are precursors to oestrogen

Role of Oestrogens in Pregnancy

• Essential For Foetal Survival (Urinary Oestrogens Decreased with Foetal Death)

• Myometrial Hypertrophy and Gap Junctions

• Lacterous Duct development

• Increase Uterine Size

• Increase External Genitalia Size

• Relaxes Pelvic Ligament

• Increase Oxytocin Receptors

A small amount is needed to maintain pregnancy but a spike at the end allows for relaxation of pelvic ligament & increased oxytocin receptors)

What type of hormone is relaxin

Peptide hormone

Where is relaxin produced

Corpus luteum & placenta in pregnancy

Also produced in the prostate

Relaxin increases secretions of what hormones

LH

hCG

Role of Relaxin in pregnancy

Myometrial Relaxation - Facilitation of Implantation

Relaxation of Pelvic Ligament

Relaxation of Cervix

Effect of relaxin on myocardial overload

Decreases it

Effect of relaxin on renal function

Increases renal function

Effect of relaxin on cell preservation

Effect of Relaxin on the ECM

Increased remodelling