Menstrual Cycle

Which hormones do the ovaries produce?

Oestrogen and Progesterone

What do we call the first ever menstrual cycle a woman experiences?

Menarche

From which gland are LH and FHS secreted?

The anterior pituitary gland.

What does the Kiss1 gene produce?

Kisspeptin

What stimulates the release of GnRH?

The binding of GPR54 with kisspeptin

How does estradiol influence kisspeptin and GnRH release?

Estradiol regulates kisspeptin differently in brain regions (inhibits in arcuate, stimulates in AVPV); kisspeptin then activates GPR54 on GnRH neurons → stimulates GnRH release → triggers LH and FSH secretion.

Which region in the brain regulates GnRH release?

The hypothalamus and specifically the anteroventral periventricular nucleus (AVPV)

What activates GnRH neurons?

Kisspeptin binding to GPR54

What activates kisspeptin?

Estradiol

When is puberty initiated?

When GnRH is secreted by hypothalamic neurons

What does GnRH stimulate the release of?

LH and FSH

FSH triggers the release of which hormone?

Estrogen

LH triggers the release of which hormone?

Progesterone

What does estrogen do?

Prepares the endometrium for pregnancy

What does progesterone do?

Maintains endometrium for implantation and inhibits further ovulation during the luteal phase

By which cells are FSH and LH secreted?

gonadotropic cells of the anterior pituitary gland

What does FSH do?

Stimulates the growth and recruitment of immature ovarian follicles in the ovary

What hormonal changes occur during the luteal-follicular phase transition that allow FSH to rise?

A decrease in progesterone and estrogen levels following corpus luteum degeneration leads to reduced negative feedback, allowing increased secretion of FSH from the anterior pituitary.

What does LH do?

It supports theca cells in the ovaries that provide androgens and hormonal precursors for estradiol production and triggers ovulation in the menstrual cycle.

When does the follicle inhibit production of estrogens?

When it has fully matured and is ready to ovulate, leading to decreased secretion of FSH.

What are the effects of estrogen on muscle, bone, and connective tissue?

Estrogen increases muscle mass and strength, enhances muscle regeneration, boosts bone density, improves exercise responsiveness, and promotes collagen synthesis in muscles, tendons, and ligaments. It can also reduce tendon stiffness, especially during menstruation.

What effects does estrogen have on the uterus?

It increases uterine growth, vaginal lubrication and thickens the vaginal wall

What effect does estrogen has on plasminogen?

It increases it

What effect does estrogen have on antithrombin III?

It decreases it

What effect does estrogen have on HDL and LDL?

Increases HDL and LDL

What effect does estrogen have on fluid balance?

It increases salt and water retention WH

What effect does etsrogen have on the GI tract?

It reduces bowel mobility (constipation) and increases cholesterol in the bile

What effect does estrogen have on melanin?

Increases pheomelanin and reduces eumelanin

What effect does estrogen have on the lungs?

Promotes their function (supports alveoli)

Which type of cells are responsible for the immediate incraese of progesterone after the LH surge serum ?

Granulosa lutein cells

What does progesterone biosynthesis require?

Cholesterol, LH stimulation, StAR protein for cholesterol transport, and key enzymes including CYP11A1 and 3β-HSD.

What are the functions of progesterone?

Enlarges breasts, assists in lobuloalveolar development, ductal development and skin health

What is Folliculogenesis?

Folliculogenesis is the maturation of ovarian follicles, starting from primordial follicles and progressing through several stages until one becomes the dominant follicle that may ovulate.

What are the stages of Menstrual Cycle?

1. Menstruation

2. Follicular Phase

3. Ovulation

4. Luteal Phase

What happens during Menstruation?

The functional layer of the endometrium sheds when ovulation is not followed by fertilization.

Which hormone increases the size of the ovaries, fallopian tubes, uterus and fallopian genitalia?

Estrogen

Which hormone promotes increased secretion by the mucosal lining of the fallopian tubes?

Progesterone

Which hormone promotes the secretory changes in the uterine endometrium?

Progesterone

Which hormone causes marked proliferation of the endometrial stroma and greatly increased development of the endometrial glands

Estrogen

Which hormone develops the stromal tissues of the breasts, helps grow the extensive ductile system and helps deposition fat in the breasts?

Estrogen

Which hormone promotes development of the tubules and alveoli of the breasts, and causes the alveolar cells to proliferate enlarge and become secretory?

Progesterone

Which hormone decreases the frequency and intensity of uterine contractions?

Progesterone

Which hormone stimulates bone growth and slightly increases protein deposition?

Estrogen

Which hormone increases body metabolism and fat deposition?

Estrogen

Which hormone causes sodium and water retention by the kidney tubules?

Estrogen

When does ovulation occur?

12hrs after the LH peak

When does the LH surge occur?

Approximately 24-36 hours before ovulation.

What does the LH surge stimulate?

The release of an egg from the ovary.

When does the proliferative phase begin?

During the ovarian follicular phase and lasts until ovulation. (from end of menstruation to ovulation)

Which hormone stimulates growth of endometrium and synthesis of progesterone receptors in endometrium?

Oestrogen

When does the secretory (pregestational) phase happen?

After ovulation and lasts until the start of menstruation. (after ovulation when new corpus luteum is formed.

What effects does progesterone have on the endometrium?

Makes it a highly vascularised glycogen filled tissue

How does progesterone affect estradiol in the luteal phase?

It decreases its activity

• it decreases the concentration of estradiol

• it increases the activity of the enzyme that’s responsible for the conversion of estradiol to estrone and

• it increases the activity of estrone sulfotransferase