Endocrinology of Pregnancy

Question 1

Where is tubular fluid reabsorbed and what controls this process?

Answer 1

Rete testis
Early epididymis
Induced by oestrogen

Question 2

Where do you find oestrogen within the male reproductive tract?

Answer 2

Tubular fluid produced by sertoli cells

Question 3

What stimulates the release of nutrients and other molecules (e.g. glycoproteins) into the epididymal fluid?

Answer 3

Androgens

Question 4

What are the roles of androgen induced secreted nutrients and molecules?

Answer 4

Nutrients provide energy for impending journey

Glycoproteins coat surface of the spermatozoon (to protect from hostile environment)

Question 5

Within which part of the male reproductive tract is fluid reabsorbed and secretory products put in?

Answer 5

Epididymis

Question 6

Why is the concentration of sperm in the vas deferens higher than further down the reproductive tract?

Answer 6

Further down the reproductive tract, other fluids + secretory products are added thus diluting the sperm.

Question 7

Which structures contribute to the seminal fluid?

Answer 7

Epididymis/testes (small contribution)
Seminal vesicle (2/3)
Prostate (1/3)
Bulbourethral glands

Question 8

What is semen comprised of?

Answer 8

Spermatazoa
Seminal fluid
Leucocytes
Potential viruses

Question 9

When do sperm achieve full activity and what is the name given to this process?

Answer 9

Capacitation

Occurs within ionic + proteolytic environment of Fallopian tube

Question 10

What 3 changes take place in capacitation?

Answer 10

Loss of glycoprotein coat
Change in surface membrane characteristics (leading to acrosome reaction when in close proximity to the ovum)
Whiplash movements of the tail

Question 11

What are capacitation changes dependent on?

Answer 11

Oestrogen

Calcium

Question 12

Describe the acrosome reaction.

Answer 12

Sperm binds to ZP3 glycoprotein on zona pellucida
Once bound, progesterone stimulates Ca2+ influx into the sperm
Causes release of hyaluronidase + proteolytic enzymes from acrosome
Results in penetration of the zona pellucida

Question 13

Where does fertilisation normally occur? What does fertilisation result in the expulsion of?

Answer 13

Fallopian tube

Expulsion of Second polar body

Question 14

The zonal reaction immediately follows fertilisation. Describe the zonal reaction.

Answer 14

Cortical granules release molecules that degrade the zona pellucida (including ZP3 + ZP2)
Prevents further binding of other sperm
Ca2+ dependent
The cell is now diploid

Question 15

How does the conceptus receives nutrients before implantation? Describe the conceptus at this point

Answer 15

Uterine secretions provide nutrients

Continues to divide as it moves down Fallopian tube

Question 16

How long is this free-living phase of the conceptus?

Answer 16

9-10 days

Question 17

In what stage of the menstrual cycle does the development of the conceptus occur?

Answer 17

Luteal phase– oestrogen + progesterone are high

Question 18

What does the conceptus compact to form?

Answer 18

8-16 cells morula

Question 19

What are the two parts of the blastocyst?

Answer 19

Inner cell mass: becomes the embryo

Trophectoderm: becomes the chorion (which becomes the placenta)

Question 20

What hormonal change facilitates the transfer of the conceptus to the uterus?

Answer 20

Increasing progesterone: oestrogen ratio

Question 21

What is a decidua?

Answer 21

Thick layer of modified mucous membrane, which lines the uterus during pregnancy + is shed after birth

Question 22

What hormone environment is required for decidualisation phase of implantation?

Answer 22

Progesterone dominance in the presence of oestrogen

Question 23

State 2 molecules that are of particular importance in implantation. Mention which cells produce these molecules.

Answer 23

Leukaemia inhibitory factor (LIF)
Produced by endometrial secretory glands
Stimulates adhesion of blastocyst to endometrial cells
IL-11
Also released from endometrial cells + into uterine fluid
Also may be involved

Question 24

In decidualisation, what endometrial changes due to progesterone occur?

Answer 24

Glandular epithelial secretion
Glycogen accumulation in stromal cell cytoplasm
Increased vascular permeability in the invasion region, associated with oedema of tissues
Growth of capillaries

Question 25

Which chemical factors are involved in decidualisation?

Answer 25

Mainly IL-11 Histamine Certain prostaglandins TGF-beta (promotes angiogenesis)

Question 26

What is the role of hCG and when does it peak?

Answer 26

Peaks at 8 weeks + is particularly important in 1st 6 weeks Mimics LH by binding to LH receptors on the corpus luteum + stimulating the production of oestrogen + progesterone Produced by trophoblast cells

Question 27

What change takes place after about 6 weeks?

Answer 27

Role of hormone production is transferred from the corpus luteum (stimulated by hCG) to the placenta

Question 28

Describe how oestrogen and progesterone levels change throughout pregnancy.

Answer 28

Oestrogen + progesterone levels continue to rise through pregnancy with progesterone always being the dominant influence

Question 29

What is the role of human placental lactogen?

Answer 29

Involved in changes in metabolism Causes insulin resistance so mother has higher glucose levels Promotes nutrients going to baby

Question 30

Which steroid precursor tends to be provided by the mother for the foetus?

Answer 30

Pregnenolone

Question 31

Which androgen is formed by the maternal and foetal adrenals? This is used as a precursor for oestrogen production.

Answer 31

Dehydroepiandrosterone Sulphate (DHEAS)

Question 32

Which oestrogens are produced by the placenta using DHEAS from the mother and foetus?

Answer 32

Oestradiol | Oestrone

Question 33

Oestradiol + Oestrone aren’t a good measure of foetal health. Explain why.

Answer 33

These oestrogens are dependent on precursor production from the both the foetal + maternal adrenals. Therefore, it is not a good measure of foetal health.

Question 34

What is the main oestrogen of pregnancy? Describe how it is produced.

Answer 34

OESTRIOL DHEAS from the foetal adrenals is conjugated in the foetal liver to form 16-alpha-hydroxy DHEAS 16-alpha-hydroxy DHEAS is then de-conjugated in the placenta + used to produce oestriol

Question 35

Describe how maternal hormones change in pregnancy.

Answer 35

``` Most increase (pituitary becomes enlarged): ACTH Corticotrophin Prolactin IGF1 Iodothyronines Adrenal steroids PTH related peptides Hormones that decrease: Gonadotrophins Pituitary GH (because placental GH variant increases towards term) TSH ```

Question 36

What biochemical change is required for contraction of the uterus during parturition?

Answer 36

Increase in intracellular Ca2+ concentration

Question 37

Describe how oestrogen increases the chance of contraction.

Answer 37

Oestrogen binds to oestrogen receptors + triggers synthesis of prostaglandins within the endometrial cells. Prostaglandins stimulate the release of Ca2+ from intracellular stores.

Question 38

Describe how oxytocin increases the chance of contraction.

Answer 38

Oxytocin binds to its receptor on the endometrial cell + opens Ca2+ channels, allowing Ca2+ ions to move in from outside

Question 39

Describe the effect of progesterone on the contraction process.

Answer 39

Progesterone keeps the effects of oestrogen under control | by inhibiting oestrogen receptors + the production of prostaglandins

Question 40

What change occurs when the foetus reaches a particular size, which is crucial for contraction to take place?

Answer 40

A switch in steroid synthesis from progesterone synthesis to oestrogen synthesis Leads to oestrogen dominance --> prostaglandin production --> Ca2+ release from intracellular stores --> promotion of muscle contraction

Question 41

What 2 hormones are involved in milk production and milk ejection?

Answer 41

Prolactin: milk production Oxytocin: milk ejection Both have a similar neuroendocrine reflex arc stimulated by suckling

Question 42

What are the 2 phases of implantation? Describe them

Answer 42

Attachment phase: Outer trophoblast cells contact uterine surface epithelium Decidualisation phase: changes in underlying uterine stromal tissue

Question 43

List 3 key roles of Oxytocin

Answer 43

Uterine contraction Cervical dilation Milk ejection

Question 44

Which hormone is produced by the foetus around the time of partruition?

Answer 44

Cortisol