Endocrinology of Pregnancy

Question 1

What are the functions of the hormones produced by the placenta?

Answer 1

Stimulate ovarian/uterine function, maintain pregnancy, module fetal growth, stimulate mammary function, assist in parturition

Question 2

What are the placental hormones?

Answer 2

Progesterone (not in all species), oestrogen, chorionic gonadotrophins, relaxin, prolactin, placental lactogen

Question 3

In which species is their placental takeover of progesterone production?

Answer 3

Cow, ewe, mare, queen and human

Question 4

What are the functions of the distinct oestrogens produced by fetal cotyledons/trophoblast cells?

Answer 4

Stimulate mammary development, placental growth and differentiation & growth of myometrium, increase uterine blood flow and prepares for parturition

Question 5

Where is relaxin produced and what are its actions?

Answer 5

Produced by CL (cow, sow) and placenta (rabbit, mare) – softens connective tissue enabling growth of fetus, relaxation of pelvic ligaments, prepares for parturition

Question 6

Where is prolactin produced and how is it regulated?

Answer 6

Produced by lactotrophs of anterior pituitary gland and placenta, inhibited by dopamine, stimulated by oestradiol

Question 7

Where is placental lactogen produced and what are its functions?

Answer 7

Produced by binucleate cells, binds to prolactin receptors, modulates fetal metabolism and stimulates mammary gland development

Question 8

What is ovarian progesterone dependent on in the bitch?

Answer 8

LH and prolactin

Question 9

When do progesterone levels in the pregnant queen differ from non-pregnant?

Answer 9

Rapid rise and divergence at 21 days

Question 10

What does plasma progesterone in the horse fall midway through pregnancy?

Answer 10

Placenta takes over, produces different progesterone like compounds which remain within the placenta, metabolised on entering circulation

Question 11

How do the endometrial cups in the mare form?

Answer 11

Form from invasion of fetal trophoblast cells

Question 12

What is caused by eCG?

Answer 12

Formation of an accessory CL & the release of placental progestogens

Question 13

What is the main progestagen produced by the equine placenta?

Answer 13

Main progestagen is 5α-pregnane

Question 14

Why is there a sudden rise in progesterone around day 50 in the ewe?

Answer 14

Placenta takes over

Question 15

What are the pregnancy lengths in the common species (in days)?

Answer 15

Cat – 63, dog – 58-72, cattle – 270, horse – 330, pig – 114, sheep – 150

Question 16

What key agents can be used in pregnancy termination?

Answer 16

PGF2α or analogue (before placenta takes over, overridden by eCG in the mare), corticosteroids (induce myometrial contractions), oestradiol (prevents zygote transport to uterus in dogs, luteolytic in ruminants – large dose in cow after 100 days), dopamine agonists (inhibit prolactin secretion)