Endocrinology of Pregnancy

Question 1

What controls tubular fluid reabsorption?

Answer 1

oestrogen

*in rate testis and epidydimid

Question 2

What controls nutrient and glycoproteins secretion into epidydimal fluid?

Answer 2

Androgen

*function - roadies energy for journey and coat the surface of the spermatozoa (protection)

Question 3

What does semen consist of?

Answer 3

Spermatozoa

Seminal fluid(from mainly accessory sex glands but minor lay from epidydimis and testes)

• seminal vesicles produce fructose and fibrinogen
• prostate produces citric aid
• Ampulla
• bulbourethral

Leukocytes

Question 4

What percentage of spermatozoa in ejaculate reach the cervix?

Answer 4

1%

Question 5

Outline the capactation of ser

Answer 5

Spermatozoa undergoes capacitation in oviduct for full activity

1. loss of glycoproteins coat
2. change in surface membrane characteristics
3. whiplash movements

*oestrogen dependent nd requires Ca2+ for all activities (hence why it occurs in oviduct)

Question 6

What happens during fertilisation?

Answer 6

Occurs in Fallopian tubes

Results in expulsion of second polar body nand leads to immediate zona reaction (degradation of ZP3 coat) to prevent further binding (Ca2+ dependent)

• G protein mediated action once ZP3 binding is established and progestrone, leads to influx of Ca2+ into sperm
• cortical reaction - breakdown of zona pellicuida by granules containing digestive enzymes to break down coat

Once diploids is established, zygote starts dividing

The spermatozoa binds to ZP3 glycoproteins and penetrates the zona pellucida releasing haluronidase

Question 7

What is the conceptus?

Answer 7

Fertilised ovum

Continues to divide as it travels Dodson the Fallopian tube - 3/4 days

• receives nutrients from uterine secretions
• phase can last 9-10 days

Question 8

Outline the development of the conceptus

Answer 8

First compacts to an 8-16 cell morula

The becomes a blastocyst (inner mass becomes embryo and outer trophoblast becomes the chorion)

Then transferrres to uterus at this stage - fcilitated by increasing prgesterone:oestrogen ratio (literal phase)

Question 9

What happens during implantation?

Answer 9

Invasive process involves:
-Attachment phase - outer trophoblast cells contact uterine epithelium

-Decidualisation of underlying stromal tissue

Requires progesterone domination in the presence of oestrogen

Question 10

What happens in the attachment phase of implantation?

Answer 10

Leukaemia inhibitory Factory (LIF) from endometrium (and blastocyst) stimulates adhesion of blastocyst to endometrium

IL-11 is also released into uterine fluid

Question 11

What happens during the desidualisation phase of fertilisation?

Answer 11

Invasion of underlying uterine stromal tissue by outer trophectoderm cells of the blastocyst

Within hours - increased vascular permeability in invasion region (oedema), localised changes in intracellular composition (glycogen accumulation in cytoplasm) and progressive sprouting and growth of capillaries (desidualisation reaction)

Factors involved:
IL-11
Histamine
Prostaglandins
TGF-beta (angiogenesis)

Question 12

What happens during pregnancy?

Answer 12

First 5-6 weeks :
Maternal ovaries realease gonadal steroids
Circulating progesterone and olestra diol concentrations are high and rising and inhibit the release of maternal LH and FSH
- as LH and FSH are inhibited, the stimulators role on the corpus outrun is taken over by hCG produced by developing blastocyst

From day 40:
Ovariectomy has no effect on pregnancy
Role of corpus luteum (production of progesterone and oestrogen) taken over by foetalplacental unit

Question 13

Describe the changes in maternal hormones

Answer 13

Increase:
-ACTH - pregnancy activates stress-axis so more ACTH (leads to more cortisol)
-prolactin - prolactin suppresses GnRH
-adrenal steroids
Iodothyronines - pregnancy increases metabolic rate - driven by hCG not TSH
- PTHrp (parathyroid hormone related peptide) - more calcium requirement for lactation
- IGF-1 - planceta also makes growth hormone

Decrease:

• Gonoadotrophin
• TSH - hCG stimulates high T4 production
• hCG - placental variant increases

Question 14

What happens during parturition?

Answer 14

Oxytocin -> raised intracellular calcium -> contraction

Contractions happen by calmodulin activating calmodulin-myosin kinase which contracts actin-myosin.

Oestrogen (progestrone inhibits this) stimulates phospholipase A2 which stimulates arachadonic acid to PGF24 production to raise intracellular calcium from microsomes. Calcium can also just enter from outside

Question 15

What happpens during lactation?

Answer 15

Prolactin stimulates milk synthesis

Oxytocin stimulates milk ejection