Hormonal Changes Before & During Pregnancy

Question 1

What is folliculogenesis?

Answer 1

The process where a recruited primordial follicle grows into a Graafian one.

Question 2

What is oogenesis?

Answer 2

The formation of egg cells, which are part if the follicle so technically, oogenesis is part of folliculogenesis.

Question 3

When do hormonal changes occur?

Answer 3

During menstrual cycle, during fertilisation, during pregnancy all the way until labour.

Question 4

What is the main function of the placenta that take place?

Answer 4

To provide efficient nutrient and oxygen supply for fetal growth.

Question 5

What is a primordial follicle?

Answer 5

A primary oocyte arrested in meiotic prophase I. Surrounded by a single layer of follicular cells without zone pellucida.

Question 6

How many primordial follicles are there during different phases of life?

Answer 6

Mid-pregnancy: 7 million
At birth: 1 to 2 million
Menstrual Cycle: 12 to 20 follicles will be stimulated to grow each cycle
At menopause: less than 1000

Question 7

How many primordial cells actually become a Graafian follicle?

Answer 7

Out of the 12 to 20, only one matures to become a Graafian follicle, and be released.

Question 8

Why is there a decrease from 7 million to 1 to 2 million primordial follicles?

Answer 8

Most of them undergo atresia and die.

Question 9

What kind of receptors do granuloma cells have?

Answer 9

They initially express FSH receptors and later on they express LH ones.

Question 10

What kind of receptors do theca cells have?

Answer 10

They express LH receptors.

Question 11

What is the process of oogenesis during the fetal period?

Answer 11

Fetal Period: Oogonium undergoes mitosis and turns into a primary follicle, meiosis is in progress and the primary oocyte is stuck at prophase I until puberty.

Question 12

What is the process of oogenesis during puberty?

Answer 12

Every month one primary oocyte completes meiosis I and it develops into one polar body a secondary oocyte. From there on meiosis II may occur to form two polar bodies.

Question 13

What is the process of oogenesis after fertilisation?

Answer 13

In the case of fertilization, the secondary oocyte completes meiosis II to produce an ovum and a second polar body.

Question 14

How is a primary oocyte arrested in meiosis I?

Answer 14

Granulosa cells release cGMP which inhibits the PDE3A enzyme in the oocyte and blocks cAMP degradation. cAMP increases and thus meiosis is arrested.

Question 15

How does meiosis I resume?

Answer 15

Pre-ovulatory LH surge inhibits cGMP production by granuloma cells which decreases cAMP production and thus resumes meiosis.

Question 16

How is GnRH released?

Answer 16

In pulses

Question 17

Menstrual Cycle Hormones Regulated

Answer 17

The patterns of pulsation of GnRH secrete specific hormones. Low-frequency pulsations favours FSH release while high-frequency favours LH release.

Question 18

Where is LH released from?

Answer 18

Corpus luteum

Question 19

Why can’t granuloma cells produce oestrogen on their own?

Answer 19

They require androgens which are produced by the theca cells.

Question 20

What changes to the receptors of the granuloma cells during the follicular phase?

Answer 20

They have FSH receptors

Question 21

What do theca cells produce?

Answer 21

Androgens

Question 22

What do granuloma cells produce?

Answer 22

Progesterones

Question 23

What is the hypothalamic-pituitary-ovarian axis?

Answer 23

A tightly regulated system controlling female reproduction

Question 24

Does oestrogen usually have positive or negative feedback?

Answer 24

Oestrogen can have both, but usually it is negative except of when it is required for ovulation, as it secretes LH.

Question 25

Explain HPO axis

Answer 25

GnRH from the hypothalamus causes release of FSH and LH from the anterior pituitary which stimulate ovarian hormones.

Question 26

What is the function of inhibin?

Answer 26

Negative feedback and it inhibits FSH secretion by the anterior pituitary.

Question 27

Which primary follicle survives?

Answer 27

The largest one, with the most FSH support.

Question 28

What causes atresia?

Answer 28

The lack of support of FSH, as large volumes of androgens are released from the dominant follicle.

Question 29

What are the functions of the placenta?

Answer 29

Support: provide nutrients and oxygen Immunity: suppress the maternal immune system to prevent immunologic rejection Endocrine: hormone synthesis, transport and metabolism

Question 30

Where does the embryo get its nutrients from prior to the formation of the placenta?

Answer 30

Trophoblastic digestion and absorption of nutrients from endometrial decidua.

Question 31

Which hormone is similar to LH during pregnancy?

Answer 31

hCG, human chorionic gonadotropin, maintains corpus luteum and secretes progesterone and oestrogen.

Question 32

Why is oestrogen higher towards the end of the pregnancy?

Answer 32

It helps with the relaxation of smooth muscle so makes labor and delivery easier.

Question 33

Which hormone is detected to present a positive pregnancy result?

Answer 33

hCG

Question 34

What effect does oestrogen have during pregnancy?

Answer 34

Enlargement of ovaries, uterine tubes, uterus, vagina, breasts and female external genitalia. It also causes renal sodium and water retention which leads to oedema and swelling.

Question 35

What is the function of progesterone during pregnancy?

Answer 35

Development of decidua, essential for nutrition, Decreases frequency of uterine contractions, less of a chance for miscarriage. Promotes development of lobules and alveoli in breasts Inhibits T lymphocyte-mediated rejection of placenta

Question 36

What is the effect of human chorionic somatomammotropin?

Answer 36

Stimulates breast development and lactation Decreases insulin sensitivity, and decreases utilisation of glucose from the mother Promotes release of free fatty acids Similar effects as prolactin and growth hormone

Question 37

Where is human chorionic somatomammotropin produced?

Answer 37

Syncytiotrophoblasts

Question 38

What is the effects of relaxin during pregnancy?

Answer 38

Inhibits uterine contraction Relaxes pubic symphysis Development of mammary glands Vasodilator, increased renal blood flow, venous return and cardiac output

Question 39

What is the effect of relaxin at the time of delivery?

Answer 39

Softens and dilates uterine cervix

Question 40

What happens to the anterior pituitary gland during pregnancy?

Answer 40

Increases 50% in size

Question 41

Which anterior pituitary hormones increase during pregnancy?

Answer 41

Corticotropin Thyrotropin Prolactin

Question 42

Which anterior pituitary hormones decrease during pregnancy?

Answer 42

FSH and LH due to high levels of oestrogen

Question 43

What happens to the adrenal cortex during pregnancy?

Answer 43

Glucocorticoids increase so synthesise tissues in the fetus. Aldosterone secretion increases so increase in renal retention so pregnancy induced hypertension

Question 44

What happens to the thyroid gland during pregnancy?

Answer 44

50% increase in size

Question 45

What happens to the parathyroid glands?

Answer 45

increase in size and produce for PTH

Question 46

Why does PTH production increase?

Answer 46

Calcium released from mother's bones moves to the fetus in order to ossify its own bones, so PTH increases to provide calcium for both