Hormones and Reproduction: Menstruation and Pregnancy

Question 1

What is the corpus luteum?

Answer 1

Corpus luteum (yellow body) – the part of the ovary from where ovulation has recently occurred

Question 2

What does the corpus luteum produce?

Answer 2

o The corpus luteum produces estrogen and progesterone.

Question 3

How long can LH maintain the corpus luteum for?

Answer 3

o LH can maintain the corpus luteum for a week……
o After that another signal is needed
o Steep decline of estrogen and progesterone then you are going to menstruate.
o If you menstruate you lose the pregnancy

Question 4

Menstruation is shedding of superficial layer (functionalis) of endometrium. Withdrawal of sex steroid support leads to:

Answer 4

o vasoconstriction
o tissue hypoxia
o connective tissue breakdown
o fragmentation

• Coagulation factors control blood loss locally

Question 5

What is endometriosis?

Answer 5

• establishment and growth of endometrial tissue outside the uterus
  terms: ectopic, eutopic (mice don’t get endometriosis)
• Escapes through fallopian tube and goes into the abdominal cavity and fragments of tissue establish themselves in various places.

Question 6

How does endometriosis arise?

Answer 6

• Much of it by reflux menstruation – endometrial tissue fragments shed at menses passing through the Fallopian tube, then becoming established in ectopic sites
• The lesions continue to cycle under hormonal control but are not lost at menstruation (as they have receptors)
• However some endometriosis cannot be explained in this way
• Alternatively it may arise de novo from progenitor cells in ectopic tissues
• It’s not clear why only some women get it – most women probably reflux menstruate to some extent
• Family history is a risk factor

Question 7

Symptoms and treatment:

Answer 7

• Endometriosis is associated with pelvic pain and infertility
• Surgery is often used to remove lesions (not done lightly)
• It can also be treated by pain medication (NSAID)
• Or by blocking pharmacologically the hormonal cycle:
o Aromatase inhibitor
o Combined oral steroid contraceptive
o Gonadotropin-releasing hormone (GnRH) modulators

Question 8

What is the blastocyst?

Answer 8

Embryonic stage that implantation takes place in lining of the womb

Question 9

What is interstitial implantation?

Answer 9

• Embryo burrows into uterus (interstitial implantation)

Embryo’s must develop to the blastocyst sage before they can implant

Question 10

When does the LH peak occur?

Answer 10

36 hours after ovulation

Question 11

What is hCG?

Answer 11

Human chorionic gonadotrophin (hCG)

• The placenta produces the polypeptide hormone hCG from the hatched blastocyst stage onwards
• It appears in measurable quantities in maternal blood (and urine) soon after implantation (used for pregnancy testing)
• hCG rescues the corpus luteum (so P continues to rise)
• Lack of timely appearance of hCG probably accounts for the ‘closure’ of the receptive period for implantation
• If implantation is too late, the CL will regress, and pregnancy fails!

Question 12

What is progesterone?

Answer 12

• regulates the rate of transport of the egg/embryo through the Fallopian tube
• prepares the uterus to receive the implanting blastocyst
• sustains the uterine lining (endometrium) throughout pregnancy

Question 13

What is the luteoplacental endocrine switch?

Answer 13

At 7-9 weeks, the placenta takes over the production of estrogen and progesterone from the corpus luteum

Question 14

When is a pregnancy described as viable?

Answer 14

Pregnancy is described as viable from when heart pulsations can be visualised within gestation sac

Question 15

Symptoms of ectopic pregnancy?

Answer 15

• abdominal pain
• hCG detected
• scan– no intrauterine body?
• ectopic pregnancy?
• tubal rupture can be fatal!
• medical management or surgery?
• methotrexate (folate antagonist, blocks DNA synthesis

Question 16

What is the law around pregnancy termination?

Answer 16

• Though the law permits terminations up to 24 weeks, the great majority are done before the 13th week.

Question 17

How does Mifepristone (RU486)?

Answer 17

• RU486 is structurally similar to P and binds the PR…but exerts very different effects, acting instead as an antagonist, for example:
– It blocks preparation of the endometrium for pregnancy
– It counteracts the suppressive effect of P on myometrial contractility

Question 18

What is Human Placental Lactogen?

Answer 18

• hPL modulates intermediary metabolism by changing the level of insulin-like growth factor (IGF)
• in turn this increases glucose and amino acid availability to the fetus

Question 19

Embryonic pregnancy=

Answer 19

up to 10 weeks, formation of major organs

Question 20

Fetal pregnancy=

Answer 20

• 10-38 weeks, maturation, development and growth

Question 21

What are CAPS?

Answer 21

CAPS are contraction-associated protein.

Progesterone suppresses myometrial contractility until late pregnancy.
Initiation of labour may be via inflammatory mediators.

Question 22

What is oxytocin?

Answer 22

• Peptide hormone (nine-mer)
  • Released from posterior pituitary
  • Levels rise in last trimester
  • Myometrial receptors increase markedly around week 36
  • Used, with PG analogues, to induce labour – look up in BNF 7.1.1

Question 23

Why is drug use in pregnancy always to be considered?

Answer 23

• Most drugs diffuse across the placenta and enter the fetal circulation to some extent
• Try to avoid all drugs in the 1st trimester
• Essential therapy taper to lowest effective dose prior to conception
• If appropriate switch to a safer drug during pregnancy
• Use lowest effective dose for minimal duration

Question 24

What % of births are premature?

Answer 24

5-10%