Endocrinology of Puberty II Flashcards
What is adrenarche?
- Occurs before puberty
-Maturation of cells in zona reticularis of the adrenal glands > selective ↑ in plasma levels of adrenal androgen precursors
- Stimulates axillary and pubic hair growth in females and males
Describe puberty in females.
- Physically
- Endocrine
- Behaviour?
- Physical: growth spurt, breast development, ↑ body fat, ↓ lean body mass, maturation of reproductive tract, …
- Endocrine: pulsatile and cyclic GnRH, LH and FSH release, cyclic pattern of estrogen and progesterone secretion, oogenesis & ovulation, menstruation
- Behavioural effects
> Menarche is a definitive but late sign of puberty and do not mean that the individual is immediately fertile
Describe the hypothalamus pituitary- ovary axis
- Negativ or positive
What changes are there in sexual behaviour for females during menstural cycle ?
- Increase in intercourse frequency around ovulation
- ↑ female libido, sexual behaviour and desire mid- cycle
- (↑ female’s “attractiveness” to males – Primates)
> Reduction in sex steroids in female (e.g. ovariectomy, menopause) can be associated with a reduction in libido in some individuals (accompanied by changes in the reproductive tract)
In humans, many other factors are involved in sexual behaviour and intercourse (e.g. personal motivation, past experiences, cultural & social factors)
Before birth:
1- What cells are present in the embryological ovary?
2- What occurs in the ovaries by 7 months gestation?
3- How are primary oocytes developed further after puberty?
1- Primordial germ cells (PGC’s)
- Migrate to the cortex of the gonadal ridge
- Divide by mitosis (oogonia)
- Stromal cells > Encircle the oogonia > Begin to differentiate (granulosa cells)
2-
- All mitotic divisions of oogonia are complete
- Meiosis - 1 is stalled at prophase = primary oocytes
- Primary oocytes are surrounded by granulosa cells forming primordial follicles
3-
- Meiosis I is completed at ovulation
- Meiosis II is completed after fertilisation
Compare the puberty stage of males and females and the effect is has on spermatogenesis and oogenesis.
What is folliculogenesis?
- The maturation of ovarian follicles
- Begins as a primordial follicle
- Becomes a graafin follicle
- Can be split into 3 stages
Describe the first phase of folliculogenesis.
Preantral phase
- Begins with the primordial follicle > Primary follicle > Secondary follicle
What happens in the second phase of folliculogenesis?
Antral phase
- Ends with a 1dominant follicle: Tertiary follicle (started with lots of different follicles)
> Changed caused by oestrogen production
What effect does FSH/LH have during antral phase?
1- Theca cells have cell surface receptors for LH only Binding = cAMP > PKA
↑supply of cholesterol to cell + ↑ rate pregnenolone synthesis = ↑ production of androstenedione
(- Pregnenolone catalyses the conversion of cholesterol to androstenedione)
Androstenedione diffuse into granulosa cells
- More LH = more androstenedione production
1- FSH receptors are found on surface of granulosa cells
2- ↑ aromatase synthesis and activity ↑ conversion androstenedione to oestradiol
* oestrogens have a mitogenic activity on granulosa cells and increase the number of FSHR. = increases granulosa cell proliferation
What happens in the third phase?
Pre-ovulatory phase
- Only occurs in the most mature follicles that have acquired LH receptors.. coincides with LH surge > produce progesterone > production of proteases which degrades tissue in the cortex of the ovary and allows the oocyte to be released.
1- When does the corpus luteum form?
2- How does the corpus luteum form?
3- What does LH signalling on granulose-lutein cells allow? What else do granulose-lutein cells produce?
4- How does LH signalling provide support?
Duration:12-15days
1- Following ovulation, the corpus luteum
forms
2- Granulosa cells stop proliferating and undergo luteinisation = Corpus luteum > Vascularisation of corpus luteum
> Granulosa-lutein cells receptive to LH now.
3-
* LH signalling on granulosa-lutein cells allows ↑ expression of LDL receptors and ↑ pregnenolone synthesis (and thus progesterone)
* Granulosa-lutein cells also produce estrogens by aromatization of androgens produced in theca-lutein cells
4-
* LH signalling provides trophic support for corpus luteum, when LH level drops > ischemia and cell death > corpus albicans
* ↓progesterone and estrogens secretion
Menstrual cycle: 1
- Describe what is taking place on the labelled arrows.
Menstrual cycle: 2
What does LH and FSH stimulate?
Menstrual cycle: 3
What does moderate rise in oestrogen + inhibin result in?
Menstrual cycle: 4
What happens to dominant follicle?
Menstrual cycle: 5
What happens during positive feedback?
Menstrual cycle 6:
What does LH surge result in? How is LH surge terminated?
What happens at ovulation to oocyte?
Menstrual cycle 7:
What does corpus lutes produce?
- No positive feedback as progesterone overrides oestrogen positive feedback with negative feedback.
Menstrual cycle 8:
What happens when LH levels decrease?
In the endometrial cycle..
What happens during the proliferative phase (follicular phase) ? (5)
-
Oestrogen-driven changes:
> ↑ proliferation of stromal cells > thickening
of endometrium
> ↑ number & size of glandular invaginations
> Endothelial cells secrete a watery mucus
> ↑ Expression of intracellular receptors to
progesterone in endometrial cells
> ↑ Myometrium excitability and contractility
= Facilitation spermatozoan transport
In the endometrial cycle…
What happens during the secretory phase? (luteal phase) (4)
-
Progesterone-driven (endometrium must be “primed” by oestrogen first)
> ↑ secretion in epithelial glandular cells > endometrial glands swollen with “uterine milk”
> Stromal cells: proliferation + predecidualization (large, round cells that store lipids and glycogen in cytoplasm)
> ↑ vascularisation of endometrium (spiral arteries)
> ↓ excitability of myometrium – limited peristalsis
= receptive and nutritive environment for conceptus
In the endometrial cycle…
What happened during the menstruation phase? (luteal> follicular phase)
- Absence of blastocyst (no hCG) & ↓ LH > corpus luteum regression > ↓ progesterone and oestrogen
- Degeneration of endometrium and its blood supply > ischemia > necrosis and shedding of functional layer
