Hormonal Changes Before & During Pregnancy Flashcards
What is folliculogenesis?
The process where a recruited primordial follicle grows into a Graafian one.
What is oogenesis?
The formation of egg cells, which are part if the follicle so technically, oogenesis is part of folliculogenesis.
When do hormonal changes occur?
During menstrual cycle, during fertilisation, during pregnancy all the way until labour.
What is the main function of the placenta that take place?
To provide efficient nutrient and oxygen supply for fetal growth.
What is a primordial follicle?
A primary oocyte arrested in meiotic prophase I. Surrounded by a single layer of follicular cells without zone pellucida.
How many primordial follicles are there during different phases of life?
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
How many primordial cells actually become a Graafian follicle?
Out of the 12 to 20, only one matures to become a Graafian follicle, and be released.
Why is there a decrease from 7 million to 1 to 2 million primordial follicles?
Most of them undergo atresia and die.
What kind of receptors do granuloma cells have?
They initially express FSH receptors and later on they express LH ones.
What kind of receptors do theca cells have?
They express LH receptors.
What is the process of oogenesis during the fetal period?
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.
What is the process of oogenesis during puberty?
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.
What is the process of oogenesis after fertilisation?
In the case of fertilization, the secondary oocyte completes meiosis II to produce an ovum and a second polar body.
How is a primary oocyte arrested in meiosis I?
Granulosa cells release cGMP which inhibits the PDE3A enzyme in the oocyte and blocks cAMP degradation. cAMP increases and thus meiosis is arrested.
How does meiosis I resume?
Pre-ovulatory LH surge inhibits cGMP production by granuloma cells which decreases cAMP production and thus resumes meiosis.
How is GnRH released?
In pulses
Menstrual Cycle Hormones Regulated
The patterns of pulsation of GnRH secrete specific hormones. Low-frequency pulsations favours FSH release while high-frequency favours LH release.
Where is LH released from?
Corpus luteum
Why can’t granuloma cells produce oestrogen on their own?
They require androgens which are produced by the theca cells.
What changes to the receptors of the granuloma cells during the follicular phase?
They have FSH receptors
What do theca cells produce?
Androgens
What do granuloma cells produce?
Progesterones
What is the hypothalamic-pituitary-ovarian axis?
A tightly regulated system controlling female reproduction
Does oestrogen usually have positive or negative feedback?
Oestrogen can have both, but usually it is negative except of when it is required for ovulation, as it secretes LH.
Explain HPO axis
GnRH from the hypothalamus causes release of FSH and LH from the anterior pituitary which stimulate ovarian hormones.
What is the function of inhibin?
Negative feedback and it inhibits FSH secretion by the anterior pituitary.
Which primary follicle survives?
The largest one, with the most FSH support.
What causes atresia?
The lack of support of FSH, as large volumes of androgens are released from the dominant follicle.
What are the functions of the placenta?
Support: provide nutrients and oxygen
Immunity: suppress the maternal immune system to prevent immunologic rejection
Endocrine: hormone synthesis, transport and metabolism
Where does the embryo get its nutrients from prior to the formation of the placenta?
Trophoblastic digestion and absorption of nutrients from endometrial decidua.
Which hormone is similar to LH during pregnancy?
hCG, human chorionic gonadotropin, maintains corpus luteum and secretes progesterone and oestrogen.
Why is oestrogen higher towards the end of the pregnancy?
It helps with the relaxation of smooth muscle so makes labor and delivery easier.
Which hormone is detected to present a positive pregnancy result?
hCG
What effect does oestrogen have during pregnancy?
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.
What is the function of progesterone during pregnancy?
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
What is the effect of human chorionic somatomammotropin?
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
Where is human chorionic somatomammotropin produced?
Syncytiotrophoblasts
What is the effects of relaxin during pregnancy?
Inhibits uterine contraction
Relaxes pubic symphysis
Development of mammary glands
Vasodilator, increased renal blood flow, venous return and cardiac output
What is the effect of relaxin at the time of delivery?
Softens and dilates uterine cervix
What happens to the anterior pituitary gland during pregnancy?
Increases 50% in size
Which anterior pituitary hormones increase during pregnancy?
Corticotropin
Thyrotropin
Prolactin
Which anterior pituitary hormones decrease during pregnancy?
FSH and LH due to high levels of oestrogen
What happens to the adrenal cortex during pregnancy?
Glucocorticoids increase so synthesise tissues in the fetus.
Aldosterone secretion increases so increase in renal retention so pregnancy induced hypertension
What happens to the thyroid gland during pregnancy?
50% increase in size
What happens to the parathyroid glands?
increase in size and produce for PTH
Why does PTH production increase?
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
