Hypothalamic-pituitary-gonadal axis II Flashcards
(32 cards)
What is puberty?
the period of sexual maturation, during which a person becomes capable of reproducing
What is puberty defined as clinically?
increased breast development in females (thelarche)
increased testicular volume in male
What are the endocrine events of puberty?
Adrenarche
Gonadarche
What is Adrenarche (6/8-15 years)?
maturation of adrenal glands
- foetal zone shrinks and definitive zone grows once foetus is born
- definitive zone releases adrenal androgens DHEA&DHEAS that cause maturation of adrenal glands (6/8-15 years old)
Where are DHEA and DHEAS synthesized?
in zona reticularis of adrenal cortex
What is the consequence of adrenarche?
Pubarche
- growth of pubic and axillary hair
- growth in height
- increased sebum production causing acne
- infection and abnormal skin keratinisation, causing acne
What is Precocious Puberty?
a condition in which puberty begins before the age of 8 in girls and 9 in boys
What is Gonadarche (11 years)?
reactivation of HPG axis and GnRH secretion
- at 16th gestational week, HPG axis is activated for sexual differentiation
- HPG axis deactivated after birth
- HPG axis reactivated during puberty (11 years)
When are the pregnancy scans?
12-13 weeks
20 weeks
At what pregnancy scan can the baby’s sex be revealed and why?
not at the 12-13 week scan, but at the 20th week scan
this is because activation of HPG axis which results in sexual differentiation is at 16th gestational week
How can we study changes in pattern of GnRH secretion?
by observing changes in pattern of LH secretion because it mimics GnRH secretion and easier to obtain
-(GnRH secreted into hypophyseal portal vein)
What is the Effect of body fat on GnRH?
Individuals with anorexia nervosa or who undergo intensive training:
- reduced response to GnRH
- decreased gonadotrophin levels
- amenorrhoea in females (absence of menstrual periods)
Restored when nourished/exercise stopped
Describe the Stimulation of onset of puberty.
kisspeptin
environmental/genetic factors
body fat/nutrition
maturation of GnRH neurones
How can leptin and ghrelin mediate puberty regulation?
they feed into hypothalamus and regulate kisspeptin, which in turn regulates onset of puberty
Describe the Inactivating mutations of KISS1 receptor or Kisspeptin gene.
Hypogonadotrophic Hypogonadism (HH) -failure to enter puberty
What is the Activating mutations of KISS1 receptor?
Precocious puberty
What is consonance?
smooth ordered progression of changes that occur during puberty
- ORDER of pubertal changes is same in everyone
- AGE OF ONSET/PACE/DURATION of changes will vary
Describe the Tanner stages of puberty.
5 stages of physical measures of development used to clinically diagnose pubertal disorders in/out of consonance based on:
1) Pubic and Axillary Hair Growth
2) Testicular Volume and Penile Length in males
3) Breast Development in females
What is a growth spurt?
Biphasic effect of oestrogen on epiphyseal growth:
>first starts with low oestrogen levels- linear growth and bone maturation
>followed by high oestrogen levels- epiphyseal bone fusion
What is a pilosebaceous unit?
structure consisting of:
>hair+hair follicle+arrector pili muscle+sebaceous gland
What are the Main types of pilosebaceous units?
Sebaceous PSU
Vellus PSU
What are the Effect of Androgens on PSUs?
Sebaceous PSU
-androgens increase sebum production, resulting in acne
Vellus PSU
-androgens differentiate vellus PSUs into:
>terminal PSUs responsible for beard growth
>APO-PSU responsible for axillary and pubic hair
What are the Psychological changes in puberty?
- increasing need for independence
- increasing sexual awareness/interest
- development of sexual personality
*later maturation is associated with better adjustment because psychological and sexual behaviours are occuring in sync
What is Precocious Puberty?
a condition in which puberty begins before the age of 8 in girls and 9 in boys
