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Medsci305 > Lecture 10: reproductive hormones, uterine contractility, and drugs > Flashcards

Lecture 10: reproductive hormones, uterine contractility, and drugs Flashcards

1
Q

What are the main hormones and their processes which regulate the menstruation cycle?

A
  • Hypothalamus releases GnRH. This acts on the anterior pituitary
  • Anterior piruitary releases FSH and LH
  • FSH in the blood and ovaries stimulates egg formation.
  • Egg maturation starts from day 4-5 and lasts until day 15.
  • At the same time gonado follicles are also releasing endogenous oestrogen which has a negative feedback on the anterior pituitary.
  • Oestrogen levels increase from the 1st day of the cycle to the 15th
  • LH activation releases the ovum. As LH levels increase, the grafian follicle ruptures which releases egg.
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2
Q

What is the basis of the mechanism of combined oral contraceptives?

A
  • Oestrogen has a negative feed back effect which depresses FSH levels.
  • If exogenous oestrogen is given via the pill, this causes a larger negative feedback of the anterior pituitary
  • Reduces FSH lessens the ovulation process
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3
Q

What are the effects of FSH after ovulation?

A

-it makes sure the endometrium is prepared for embedding of the fertilised ovum

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4
Q

How does the role of FSH differ in the first and second half of the menstural cycle?

A

first half: it facilitates oestrogen

second half: progesterone is present which has a negative feedback on the anterior pituitary and hypothalamus

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5
Q

When does progesterone take over as the dominant hormone in the menstural cycle?

A
  • from days 14-28.

- i.e. the luteal phase

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6
Q

When is the FSH and LH surge?

A

-this occurs on the 14th day.

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7
Q

What is oestrogen?

A
  • an endogenous hormone
  • oestradiol is the main hormone involved in mensturation, but there is also oestrone and oestriol
  • facilitates and enhances ability of progesterone receptors in the uterus
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8
Q

How do the effects of giving oestrogen differ when given at pre-puberty, post-puberty and post-menopause stages?

A

Pre-puberty: results in development of secondary sexual characteristics

post puberty: contraception

post menopause: stops the menopause symptoms.

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9
Q

What is the molecular mechanism of oestrogen?

A
  • oestrogen is bound to steroid flobules in the protein and metabolised in the liver
  • it is an anabolic hormone and a byproduct will form tesosterone
  • Oestrogen also increases the mobilisation of HDL
  • so someone on oestrogen has richer HDL in the blood.
  • the steroid hormone enters the cell’s nucleus and changes the genome.
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10
Q

What is the mechanism of oral contraceptives?

A
  • act viat the alpha and beta receptors
  • also have vasodilatory actions and a drop in BP
  • oestrogen is rapidly metabolised in the liver
  • side effects include extension of action and can cause genital malfunction in pregnancy.
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11
Q

What are oestrogen receptor modulators?

A

-these block endogenous oestrogen or blocks the selective roles of oestrogen e.g. raloxifen, tamoxifen, clmiphene

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12
Q

What is raloxifen used for?

A

it is a selective oestrogen receptor modulator used in carcinomas.
-it also has a metabolic protective effect

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13
Q

What is tamoxifen used for?

A

-it is an antioestrogenic used in breastcancer

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14
Q

What is clomiphene used for?

A
  • it is also an antioestrogenic and stops oestrogen binding in the pituitary.
  • blocks the alpha and beta oestrogen recpetors at hypothalamus and anterior pituitary so there is no negative feedback to shut off ovulation
  • this results in more ovulation and increases chance of more conception.
  • important for sexual development
  • metabolised in the liver
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15
Q

What is progesterone?

A
  • as well as being predominant in the second half of the menstural cycle, it is also released after fertilisation
  • it is formed at the corpus luteum as well as in the placenta
  • it is also a steroid hormone and will change gene expression
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16
Q

What is endogenous progesterone known as ?

A

hydroxy-progesterone

-medroxy-progesterone

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17
Q

What is the synthetic preparation of progesterone?

A
  • norgesterol. This can be taken orally.
  • it is weakly androgenic like oestrogen so will have problems with acne, fluid retention, weight gain and breaththrough bleeding
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18
Q

What is anti-progesterone drugs like mifepristone used for?

A

the surgical terminal of pregnancy

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19
Q

What is the combined oral contraceptive?

A
  • combined pill which contains oestrogen and progesterone.

- there is also the progesterone only pill for people that are contraindicated to take oestrogen

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20
Q

What conditions would contraindicate a woman to take the combined OC?

A

-family history of

  • hypertension
  • cvd
  • lipid disorder
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21
Q

how is the combined OC given?

A

in tablets taken in 21 day cycles with 7 day rests to establish artificial bleeding.

22
Q

What is the effect of the 21 day active pill and 7 day inactive pill cycle?

A

-enhances contraceptive power (?)

23
Q

What are the side effects of the COC?

A
  • multiple contraindications if the patient has androgenic side effects
  • weight gain
  • CVD
  • DVT
  • mild nausea
  • flushing
  • dizziness
  • depression
  • irritability
  • skin changes (acne or increased pigmentation)
  • amenorrhoea or variable duration on cessation of taking the pill
  • the extension of the combined OC might last for a certain time so need to be aware of this when trying for children.
24
Q

What is the progesterone only pill?

A
  • for women contraindicated to taking the combined oral contraceptive
  • works by primarily acting on cervical mucous to make it inhospitable to sperm
  • however the risk is that there are more chances of etopic pregnancies
  • it is metabolised in the liver so if you are on rifampacin, carmapazine, phenytoin or amoxicillin there will be some interaction as these drugs are metabolised faster so their effectiveness is reduced
25
Q

What is the emergency contraceptive pill?

A
  • this can be a progesterone only pill, or oestrogen only pill or a combined pill
  • it is effective within 72 hours and should be repeated 12 hours later
  • the reliability of the progesterone only pill means that an intrauterine device is more effective
26
Q

What are the prescribing guidelines for prescribing an oral contracepte?

A
  • take full personal and family history
  • remove all absolute and relatve contraindications
  • assess risk factors like DVT, other pills, previous history of OC, smoking
  • always do a BMI, BP, family history, migraines, especially in patients on COC or oestrogen as it has a vasodilatory effect.
27
Q

How does uterine smooth muscle contract?

A
  • presence of calcium ions binds to calmodulin, which when activated, causes actin and myosin to bind together to form cross bridges to contract and relax.
  • when the myosin heads rotate, the actin fibres slide on myosin
  • myosin is linked by gap junctions so everything contracts at the same time to have a forceful contraction.
28
Q

How is uterine smooth muscle relaed?

A

-remove the calcium by means of SERCA or sodium calcium exchangers

29
Q

How can calcium entry into uterine smooth muscle be increased?

A
  • via passive entry
  • voltage operated
  • agonist operated
  • endothelial receptors
  • prostaglandins
  • second messengers
30
Q

Where is oxytocin released from?

A

-the hypothalamus. It causes the contraction of uterine muscles

31
Q

How does protein kinase A relax uterin activity?

A
  • PKA is activated by increased cAMP which occurs as a result of beta 2 adrenoreceptor stimulation
  • PKA phosphorylates MLCK so it has less affinity for calcium and calmodulin
  • there is less phosphorylation –> relaxation
  • corticotrophin releasing hormones, parathyroid hormones, nitric oxide, all cause uterine relaxation
32
Q

How does progesterone prevent uterine contraction?

A
  • this depresses the uterine activity.
  • decreases oxytocin receptor activity and increases the amount of prostaglandin dehydrogenase
  • all of these makes sure the uterus with the foetus is relaxed
33
Q

What happens to the uterus when it is time for labour?

A
  • oxytocin and prostaglandins increase the calcium ions within the uterine muscle layer causing contraction
  • oestrogen also increases oxytocin receptors in the uterus.
34
Q

What are tocolytic agents?

A
  • drugs that prevent uterine contraction
  • e.g. progesterone,
  • beta adrenergic agonist
  • calcium channel blocker
  • oxytocin receptor antagonist
  • prostaglandin inhibitors
  • magnesium
35
Q

How is progesterone clinically used in preterm labour?

A
  • it is effective as a prophylaxis in patients with a high risk of preterm labour
  • but requires early prediction and long term treatment
  • if you are giving endogenous progesterone there is a chance of foetal abnormality so you need to monitor carefully
36
Q

How do beta adrenergic agonists treat pre-term labour?

A
  • e.g. salbutamol
  • activates the Beta 2 adrenorecetors in uterine smooth muscle and increases cAMP activity and PKA to inhibit contractility
  • but can also cause tachycardia, increased heart rate, hypotension, pulmonary oedema
  • was historically the drug of choice
37
Q

What is now the therapeutic drug of choice of tocolytic agents?

A

calcium channel blockers like nifedipine.

  • block calcium entry into the uterine cell so that there is no calcium to bind to calmodulin to cause contraction
  • also has systemic effects like hypotension, headaches, vasodilation, nausea and vomiting.
38
Q

How do prostaglandin inhibitors like NSAIDs work as tocolytic agents?

A
  • e.g. indomethacin, sulindac, nimesulide, rofecoxib.
  • blocks prostaglandin (E2 and GF2alpha) formation
  • reduces intracellular calcium and inhibits contractility.
  • also effects in fetal membranes and cervix due to presence of receptors
  • may cause arteriosus, alter renal functio in baby, but short duration of treatment is okay
39
Q

What are drugs used for promoting contraction?

A
  • prostaglandins
  • oxytocin
  • Ergometrine
40
Q

What is the clinical reason to promote uterine contraction?

A
  • Termination of pregnancy
  • inducing/augmenting labour
  • preventing post partum haemorrhage
41
Q

Howdo prostaglandins work in promoting contraction?

A
  • PGE2, PGE1 and PGEF2alpha act on PG receptors in the uterux, cervis and fetal membranes to increase contractiliy and promote cervical ripening.
  • e.g. DInoprostone (PGE2) Gemeprost and Misoprostol (PGE1) and Carboprost (PGF2alpha) analogues used
42
Q

Which drugs are used in the termination of pregnancy?

A

Gemeprost and Misoprostol (PGE1 analogues)

-these are often used in combination with an anti-progesterone such as Mifepristone

43
Q

Which drugs are used in the induction of labour at term?

A

Dinoprostone (PGE2)

44
Q

Which drugs are used to treat post partum haemorrhage?

A

Misoprostol (PGE1)

Carboprost (PGF2alpha)

45
Q

What are the side effects of prostaglandin use?

A
  • nausea, vomiting, diarrhoea
  • pyrexia (misoprostol particularly)
  • pain and bleeding
46
Q

What is ergometrine?

A
  • an ergot alkaloid (derived from fungi)
  • produces intense uterine contraction
  • acts as alpha 1 adrenergic receptor agonist, stimulates IP3 and DAG… etc.
  • usually given with syntocinon
47
Q

When is ergometrine used?

A
  • prevention of post partum haemorrhage

- treatment of postpartum haemorrhage

48
Q

What are the side effects of ergometrine use?

A
  • hypertension (avoid ergometrine with preeclampsia)
  • angina (coronary artery vasospasm)
  • headache
  • nausea, vomiting, diarrhoea
  • pain (from uterine contraction)
49
Q

What are the disadvantages of using tocolytic drugs?

A

Although they are effective at delaying delivery, they are not good at preventing preterm birth.
They have potential maternal and fetal side effects

50
Q

What is PPH?

A

post partum haemorrhage.

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