11. Endocrinology of Pregnancy Flashcards
what is on either side of the prostate?
seminal vesicles
what are sertoli cells?
cells that make spermatozoa
what are leydig cells?
cells that make testosterone
what does aromatisation of testosterone result in and what is this hormone required for?
production of oestrogen
required in men for tubular fluid reabsorption and for bones
what occurs in men and women with aromatase deficiency?
men - infertile, osteoporosis. grow tall because oestrogen is required to close growth plates.
women - virilisation: hirsutism, deepening voice, amenorrhoea.
where is most tubular fluid reabsorbed?
within the rete testis and early epididymis
where is oestrogen mainly found?
in tubular fluid produced by sertoli cells
what are secretory products (fructose & glycoproteins) secreted into and what do they do?
secreted into the epididymal fluid to
- provide energy for impending possible journey
- coat the surface of the spermatozoa to protect them from hostile environments
what does semen consist of?
- spermatozoa (15-120 million/ml)
- seminal fluid (2-5ml)
- leucocytes
- potentially viruses (e.g. hep B, HIV)
what is seminal fluid contributed from?
small contribution: epididymis and testis
main contribution: accessory sex glands - seminal vesicles, prostate, bulbourethral glands
what is seminal fluid concentrated using?
androgens
what are the qualities of spermatozoa from the semineferous tubule?
quiescent and incapable of fertilising an ovum
what are the qualities of spermatozoa from the vas deferens?
capable of limited movement, limited capability of fertilising the ovum
where is full activity (capacitation) of the spermatozoa achieved?
within the ionic and proteolytic environment of the female reproductive tract - specifically the fallopian tube
what are the 3 main stages of capacitation?
- they lose their glycoprotein ‘coat’
- change in the surface membrane characteristics
- develop whiplash movements of tail
what is capacitation dependent on?
- oestrogen: needs to happen in the female
- Ca2+
what is the acrosome reaction?
changes in the surface membrane when in close proximity to the ovum:
- sperm acrosome binds to ZP3 (glycoprotein receptor)
- Ca2+ influx into sperm (stimulated by progesterone)
- release of hyaluronidase (breaks down polysaccharides) and proteolytic enzymes
- spermatozoan can then penetrate the zona pellucida (glycoprotein layer surrounding plasma membrane of oocyte) to get to the egg
what happens when the sperm binds during fertilisation?
a cortical reaction is triggered in the zona pellucida which blocks more sperm from binding
what is a second polar body and when does it occur?
it is a small haploid cell formed during oogenesis and it occurs during fertilisation
one of the cells (ovum) retains the cytoplasm during meiotic cell division while the other (‘polar body’) has no cytoplasm and undergoes degeneration
what is the free-living phase, how long does it last and what does it involve?
the free-living phase is the phase where the conceptus (fertilised egg) is not attached yet, which occurs in the luteal phase when oestrogen and progesterone is high
it can last 9-10 days
the conceptus continues to divide as it moves down the fallopian tube to the uterus and it receives nutrients from the uterine secretions
describe the process of compaction
the 8-cell conceptus compacts to form an 8-16 cell morula
what is formed after a morula?
a blastocyst: the inner cell mass becomes the embryo and the outer trophoblast cells become the chorion (which eventually becomes the placenta)
describe the attachment phase of implantation and what it allows
the outer trophoblast cells make contact with the uterine surface epithelium
this develops a system where nutrients from the mother can be received by all the embryonic cells
describe the decidualisation phase of implantantion
decidua = thick layer of modified mucus membrane
this phase involves changes of the underlying uterine stromal tissue which lines the uterus during pregnancy and is shed with afterbirth, which requires progesterone domination
what 2 molecules are particularly important in the attachment phase? describe them
- leukaemia inhibitory factor (LIF) stimulated by Transforming Growth Factor, leptin, progesterone
- from endometrial secretory glands
- stimulates adhesion of the blastocyst to the endometrial cells - interleukin-11 (IL-11) stimulated by IL1, Tumour Necrosis Factor, Relaxin
- released from endometrial cells
- released into the uterine fluid
describe what happens during the decidualisation reaction
endometrial changes due to progesterone
- glandular epithelial secretion (nutrients)
- glycogen accumulation in stromal cell cytoplasm
- growth of capillaries to increase blood supply
- increased vascular permeability
what factors are involved in the decidualisation reaction?
- IL-11
- histamine
- certain prostglandins
- TGFb
how does hCG change during pregnancy?
hCG goes up as it takes over the role of LH
it is produced in the placenta and the surge is measurable 2 weeks from conception using a pregnancy test or earlier using a blood test
how do oestrogen and progesterone change during pregnancy?
increase
first 40 days: progesterone and oestrogen are produced in the corpus luteum, stimulated by hCG acting on LH receptors - this is essetial for developing the fetoplacental unit. oestrogen inhibits maternal LH&FSH but hCG overrides this
after day 40: placenta starts to take over oestrogen and progesterone production, it is no longer driven by LH/FSH/hCG
what is DHEAS and what is its role?
a precursor molecule (dehydroepiandrosterone sulfate) produced by maternal and foetal adrenals
it is taken up by the placenta to produce oestradiol, and is used to make small amounts of oestrone (though these also come from the mother)
how do foetal adrenals make DHEAS?
the mother provides the precursor which tends to be pregnenolone which is used to produce progesterone which the adrenals use to make DHEAS
what is the main oestrogen of pregnancy and how is it made?
oestriol
DHEAS is conjugated in the foetal liver to form 16a-hydroxy DHEAS, which goes to the plancenta and is deconjugated to form oestriol
which maternal hormones increase during pregnancy?
- ACTH
- adrenal steroids
- prolactin
- IGF1 (placenta makes GH)
- iodothyronines (hCG shares an a-subunit with TSH)
- PTH related peptides
which maternal hormones decrease during pregnancy?
- gonadotrophins
- pituitary GH
- TSH
what produces kisspeptin and what is its role?
the placenta produces kisspeptin
its role is to switch off the reproductive axis by down-regulation. it is also an antimetastatic protein, regulating the invasion of the placenta into the endometrium
how can you assess whether a woman is ovulating?
- day 21 progesterone test
- ultrasound test
how does parturition (giving birth) involve endocrine control?
- parturition involves contraction of actin and myosin filaments so requires increased intracellular calcium
- this increase is driven by oestrogen and inhibited by progesterone
- oestrogen stimulates production of prostaglandins by the endometrial cells
- the prostaglandins stimulate the production and release of calcium into the cytoplasm from intracellular stores
- oestrogen also stimulates oestrogen receptors on the endometrial cells
- progesterone inhibits prostaglandin synthesis and inhibits oestrogen receptors, so keeps the effects of oestrogen under control
what else is released at parturition and why?
oxytocin binds to its receptors which opens calcium channels, allowing calcium ions to move in from the outside
how does lactation involve endocrine control?
breast-feeding involves prolactin (promotes milk synthesis) and oxytocin (promotes milk ejection), which are stimulated by the same neuroendocrine reflex arc
the neural pathways of nipple stimulation go to the hypothalamus and pituitary gland. the pituitary gland makes prolactin in the adenohypophysis and oxytocin in the neurohypophysis
what does hypogonadropic mean?
low LH/FSH
what does hypergonadotropic mean?
low testosterone/oestrogen
