Endocrinology of pregnancy Flashcards
what hormone controls tubular fluid reabsorption from the testis to epipdymis?
oestrogen
what hormone controls nutrient and glycoprotein secretion in to epididymal fluid?
androgen
function of epididymal fluid?
Provide energy for journey and coat the surface of the spermatozoa (protection).
what does semen consist of?
o Spermatozoa – 50-150x106/ml.
o Seminal fluid – 2-5ml (made in the prostate)
o Leucocytes
o potentially viruses, e.g. hepatitis B, HIV.
where is seminal fluid produced? [2]
which has the smaller contribution?
Epididymis/testes (small contribution): including inositol and glycerylphosphorylchline.
Accessory sex glands (major contribution)
• Seminal vesicles – produce fructose and fibrinogen.
• Prostate – produce citric acid (Ca2+ chelator, acid phosphatase, fibrinogenase).
• Ampulla.
• Bulbourethral.
how much of the spermatozoa enter the cervix?
1%
how does the sperm differ in its capability to fertilise depending on location?
seminiferous tubule: incapable
vas deferens: capable of movement, little capability to fertilise
how do sperm become ready to fertilise?
after capacitation in the oviduct
what is the process of capacitation?
o Loss of glycoprotein coat.
o Change in surface membrane characteristics.
o Whiplash movements.
what is the process of capacitation dependent on?
oestrogen and Ca2+
where does fertilisation occur?
in fallopian tubes
what is the result of fertilisation
- explusion of the second polar body after undergoing second meiosis
- degradation of ZP3 to prevent further binding (calcium dependent where Gp mediated action and progesterone enable influx of calcium)
- cortical reaction, breakdown of zone pellucida by digestive enzymes
what happens when spermatozoa bind to ZP3
penetrate zona pellucida by releasing haluronidase
what is the conceptus
fertilised ovum
transformation of the conceptus along the fallopian tube
o Conceptus continues to divide as it travels down the fallopian tubes (oviduct) – 3-4 days.
o Receives nutrients from the uterine secretions.
o This phase can last from 9-10 days.
o The conceptus first compacts to an 8-16 cell morula.
o Then it becomes a blastocyst – 2 separate cell populations; inner mass (becomes the embryo) and outer trophoblast (becomes the chorion).
what is the final stage of development of the conceptus
transfer to uterus to bind to endometrium
facilitated by increased progesterone: oestrogen ratio in the luteal phase
what are the two processes that occur in implantation
o Attachment phase – outer trophoblast cells contact uterine epithelium.
o Decidualisation – of underlying stromal tissue.
this requires progesterone dominance in the presence of oestrogen
what two substances enable attachment of the conceptus to the uterus?
o Leukaemia Inhibitory Factor (LIF) from endometrium (and blastocyst) stimulates adhesion of blastocyst to endometrium.
o IL-11 is also released into uterine fluid (may be involved).
what happens in decidualisation?
Invasion of underlying uterine stromal tissue by outer trophectoderm cells of the blastocyst.
what are the changes in decidualisation?
Within hours:
increased vascular permeability in invasion region (oedema)
localised changes in intracellular composition (glycogen accumulation in cytoplasm)
progressive sprouting and growth of capillaries
(the DECIDUALISATION reaction).
factors involved in decidualisation
IL-11
histamine
prostaglandins
TGF-beta (angiogenesis).
what happens in the first 5-6 weeks of pregnancy in terms of gonadal steroids?
o Maternal ovaries release gonadal steroids.
o Circulating progesterone and oestradiol concentrations are high and rising and inhibit the release of maternal LH and FSH.
- As LH and FSH are inhibited, the stimulatory role on the corpus luteum is taken over by hCG produced by the developing blastocyst.
from day 40
o Ovariectomy has no effect on pregnancy.
o Role of corpus luteum taken over by foetalplacental unit.
which maternal hormones increase?
o ACTH – pregnancy activates stress-axis so more ACTH.
o Prolactin – prolactin supresses GnRH.
o Iodothyronines – pregnancy increases metabolic rate. Driven by hCG and NOT TSH, which is why TSH falls.
o Adrenal steroids – more ACTH thus more cortisol.
o PTHrp (parathormone related peptide) – more calcium requirement for lactation.
which maternal hormones decrease?
o Gonadotrophins –LH and FSH
o TSH – falls as hCG stimulates high T4 production instead
o hCG – placental variant increases.
how does oxytocin enable parturition?
increases intracellular calcium to enable contractions of myometrium
how does oestrogen enable the increase in intracellular calcium
Oestrogen (progesterone inhibits this) stimulates phospholipase A2 which stimulates arachidonic acid to PGF2a production to raise intracellular calcium from microsomes. Calcium can also just enter from outside.
how does contraction occur in parturition
Contraction occurs by calmodulin activating calmodulin-myosin kinase which contracts actin-myosin.
what hormone stimulates milk ejection?
oxytocin
which hormone stimulates milk synthesis?
prolactin
what is the cortical reaction?
granule molecules degrade the zona pellucida (fertilisation triggers this)
what does the conceptus become when it moves down tubes?
morula–> blastocyst
what mediator stimulated blastocyst adhesion to the endometrium?
Leukaemia inhibitory factor
what mediatory is involved in decidualisation?
IL-11
what are some changes in the decidualisation stage of attachment?
- Glandular epithelial secretion
- Glycogen accumulation in stromal cell cytoplasm
- Growth of capillaries
- Increased vascular permeability (oedema)
- Involves IL11, histamine, prostaglandins, TGFb (promotes angiogenesis)
what hormones allow parturition?
oxytocin
what else apart from oxytocin can bind to the oxytocin receptor to stimulate contraction?
foetal cortisol
placental oestrogen
oestrogen also increases calcium to lead to contraction
what are the hormones involved in…
- milk synthesis
- milk ejection ?
- milk synthesis–> prolactin
- milk ejection–> oxytocin
