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Endocrinology > Endocrinology of Pregnancy > Flashcards

Endocrinology of Pregnancy Flashcards

1
Q

Where is tubular fluid reabsorbed and what controls this process?

A
  1. Rete testis
  2. Epididymis
    This is under the control of oestrogen
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2
Q

Where do you find oestrogen within the male reproductive tract?

A

Tubular fluid produced by sertoli cells

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3
Q

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

A

Androgens

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4
Q

What are the roles of these secreted nutrients and molecules?

A
  1. Provide energy for the impending journey

2. Coat the surface of the spermatozoon (to protect them from the hostile environment)

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5
Q

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

A

Epididymis

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6
Q

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

A

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

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7
Q

Where is a vasectomy performed?

A

Lower end of the vas deferens

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8
Q

Which structures contribute to the seminal fluid?

A

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

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9
Q

Why is there fibrinogen and fibrinolytic enzymes in the seminal fluid?

A

After ejaculation, the semen initially clots and then must be broken down

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10
Q

Describe the capability of the spermatozoa in the seminiferous tubule.

A

Quiescent and incapable of fertilising an ovum

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11
Q

Describe the capabilities of the spermatozoa in the vas deferens.

A

Capable of limited movement

Limited capability to fertilise an ovum

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12
Q

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

A

Capacitation

This occurs within the oviduct (Fallopian tubes)

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13
Q

What 3 changes take place in the capacitation of sperm?

A
  1. Loss of glycoprotein coat
  2. Change in surface membrane characteristics (leading to acrosome reaction when in close proximity to the ovum)
  3. Whiplash movements of the tail
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14
Q

What are all these changes in capacitation dependent on?

A

Oestrogen

Calcium

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15
Q

Describe the acrosome reaction.

A
  1. Spermatozoon binds to ZP3 glycoprotein on the zona pellucida
  2. Once bound to ZP3, progesterone stimulates calcium influx into the spermatozoon
  3. This results in a calcium-dependent acrosome reaction
  4. This enables an exposed spermatozoon recognition site to bind to ZP2
  5. Once bound to ZP2, the acrosome releases hyaluronidase & proteolytic enzymes allowing penetration of the zona pellucida so that the head of the spermatozoon can enter the ovum
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16
Q

Where does fertilisation normally occur?

A

Fallopian tube

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17
Q

What does fertilisation result in the expulsion of?

A

Second polar body (of ovum)

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18
Q

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

A

-triggers cortical reaction
1. Cortical granules release molecules that degrade the zona pellucida (including ZP3 and ZP2)
-This prevents further binding of other sperm as no receptors
This is also CALCIUM dependent

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19
Q

Describe how the conceptus receives nutrients before implantation.

A

Uterine secretions

conceptus is the fertilised ovum

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20
Q

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

A

9-10 days

21
Q

In what stage of the menstrual cycle is all of this occurring?

A

Luteal phase – oestrogen and progesterone are high

22
Q

What does the conceptus compact to form?

A

8-16 cells morula

23
Q

What are the two parts of the blastocyst formed by the morula?

A

Inner cell mass – becomes the embryo

Trophectoderm – becomes the chorion (which becomes the placenta)

24
Q

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

A

Increasing progesterone: oestrogen ratio (luteal phase)

25
Q

What is a decidua?

A

Thick layer of modified mucous membrane, which lines the uterus during pregnancy and is shed with afterbirth

26
Q

What hormone environment is required for implantation?

A

Progesterone dominance in the presence of oestrogen

27
Q

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

A
  1. Leukaemia inhibitory factor (LIF)
    - Produced by endometrial secretory glands
    - Stimulates adhesion (attachment) of blastocyst to endometrial cells
  2. IL-11
    - Also released from endometrial cells and released into uterine fluid
28
Q

When the trophoblast cells of the blastocyst invade the underlying uterine stromal tissue, you get a decidualisation reaction. What main changes take place in decidualisation?

A

Endometrial changes due to progesterone
– Glandular epithelial secretion
– Glycogen accumulation in stromal cell cytoplasm
- Growth of capillaries
– Increased vascular permeability (→oedema)

29
Q

Which chemical factors are involved in decidualisation?

A

Mainly IL-11
Histamine
Certain prostaglandins
TGF-beta = promotes angiogenesis

30
Q

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

A

Peaks at 8 weeks and is particularly important in the first 6 weeks
It mimics LH by binding to LH receptors on the corpus luteum and stimulating the production of oestrogen and progesterone
NOTE: hCG is produced by trophoblast cells

31
Q

What change takes place after about 5 weeks?

A

From fay 40- The role of hormone production is handed over from the corpus luteum to the placenta

32
Q

Describe how oestrogen and progesterone levels in the first 40 days of pregnancy

A

Produced in corpus luteum (in maternal ovary)
• stimulated by hCG (produced by trophoblasts) and acts on LH receptors
• Essential for developing fetoplacental unit
• Inhibits maternal LH & FSH (-ve feedback)

33
Q

What is human placental lactogen? Describe its roles.

A

It is a growth hormone that has prolactin like effects

It is important for the growth and development of the foetus

34
Q

After what point would oophorectomy have no effect on pregnancy and why?

A

(surgical removal of one or both ovaries; ovariectomy.)

After around 6 weeks (40 days)
By this point the placenta would have taken over the role of hormone production so the ovaries are no longer needed

35
Q

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

A

Pregnenolone

36
Q

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

A

Dehydroepiandrosterone Sulphate (DHEAS)

37
Q

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

A

Oestradiol

Oestrone

38
Q

These two oestrogens aren’t a good measure of foetal health. Explain why.

A

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

39
Q

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

A

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 and used to produce oestriol

40
Q

What can be measured to gage the health of the foetus?

A

Oestriol: oestradiol + oestrone levels
Oestriol: total oestrogens

41
Q

Describe how maternal hormones change in pregnancy.

A

Most hormones increase in pregnancy (the pituitary gland becomes enlarged)
Hormones that increase:
- ACTH (pregnancy activates stress axis)
- Adrenal steroids (more ACTH thus more cortisol)
- Prolactin (prolactin suppresses GnRH)
- IGF1 (stimulated by placental GH-variant)
- Iodothyronines (preganayc increases metabolic rate- driven by hCG and not TSH which is why TSH falls)
- PTH (parathyroid hormone) related peptides (more calcium requirement for lactation)

Hormones that decrease:

  • Gonadotrophins
  • Pituitary GH (because placental hGH variant increases towards term)
  • TSH (falls as hCG stimulates high T4 production)
42
Q

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

A

Increase in intracellular calcium concentration

43
Q

Describe how oestrogen increases the chance of contraction.

A

Oestrogen stimulates phospholipase A2 which stimulates arachidonic acid to PGF2a (prostaglandin f2 alpha) production to raise intracellullar calcium from microsomes.

44
Q

Describe how oxytocin increases the chance of contraction.

A

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

45
Q

Describe the effect of progesterone on this contraction process.

A

Progesterone keeps the effects of oestrogen under control
Progesterone inhibits oestrogen receptors
Progesterone inhibits the production of prostaglandins

46
Q

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

A

There is a switch in steroid synthesis from progesterone synthesis to oestrogen synthesis
This leads to oestrogen dominance –> prostaglandin production –> calcium release from intracellular stores –> promotion of muscle contraction

47
Q

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

A

Prolactin – milk production
Oxytocin – milk ejection
These both have a similar neuroendocrine reflex arc stimulated by suckling

48
Q

What phases does implantation involve?

A
  1. Attachment phase - outer trophoblast cells contact uterine surface epithelium
  2. Decidualisation - changes in underlying uterine stromal tissue (within a few hours)

Endocrinology (18 decks)

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