Reproduction: Hypothalamic/Pituitary/Gonadal Axis II Flashcards
What is puberty?
Transition from a non-reproductive to a reproductive state in both males and females
What is the clinical defintion of puberty in both males and females?
- Clincal definition in females is breast development
- Clinical defintion in males is increased testicular volume
What are the 2 endocrine events that contribute to puberty?
- Adrenarche
- Gonadarche
What event is induced once as a result of adrenarche?
Puberarche
What is Adrenarche?
A change in adrenal androgen secretion due to the remodelling of the adrenal gland
What are the main adrenal androgens that see an increase in secretion as a result of adrenarche?
- Dehydro-epiandrosterone (DHEA)
- Dehydro-epiandrosterone sulphate (DHEAS)
During adrenarche does the level of secretion in another other adrenal androgen change apart from DHEA and DHEAS?
No, only secretion of DHEA and DHEAS is changed (increased) durinf adrenarche
What area of the adrenal cortex are DHEA and DHEAS produced and secreted on?
Zona reticularis of adrenal cortex
What is puberarche?
The appearance of pubic hair/axillary hair due to the increase in adrenal androgen secretion durinf adrenarche
What process is puberarche associated with?
Increased sebum production which reults in acne
What other reasons are there for the acne seen during puberarche?
- Infection
- Abnormal keratinization of the skin
What is Gonadarche?
- The reactivation of the HPG axis at puberty
- Gradual increase in pulsatile release of GnRH which results in the production of viable gametes
Why does the HPG axis need to be reactivated as a result of Gonadarche?
- HPG axis fist activates at 16th gestational week to ensure correct sexual differentiation
- Remains active during first 2 postnatal years and then shuts down for about 10 years
- HPG axis needs to be reactivated via maturation of GnRH neurons to ensure production of mature gametes
Why is LH used to study the behaviour of GnRH within the body rather than GnRH itself?
- LH mimics behaviour of GnRH within the body
- GnRH only released into hypophyseal portal circulation so incredibly difficult to take GnRH samples directly
Describe the pattern of GnRH release throughout puberty
- Reactivation of HPG axis during early puberty first results in nocturnal rise in GnRH release
- THis then gradually causes an increase in GnRH pulsatile release throughout the day until you get a consistant pulsatile release of GnRH throughout 24 hours during late puberty
- Nocturnal rise stil present at late puberty