sexual differentiation in puberty Flashcards
What is the definition of puberty?
the physiological, morphological, and behavioural changes as the gonads switch from infantile to adult forms.
What is the definitive sign of the start of puberty for boys and girls?
Females- first menstrual bless
Males- first ejaculation (often nocturnal)
Three stages of adolescent growth spurt
- The ‘age at take-off’ is the period of minimum growth velocity that immediately precedes the growth spurt
- Peak height velocity
- Time of decreased growth velocity and cessation of growth which occurs at the fusion of the epiphysis
Effect of LH in males during puberty
LH will act at the Leydig cells in males, re-initiating testosterone release from these cells they will have been dormant since their function in-utero
Effect of LH in females during puberty
Act at the Theca cells in females, causing a release of androgens that will be aromatased to oestrogen in the Granulosa cells
Effect of FSH in males and females during puberty
• FSH will act at Sertoli cells in males and Granulosa cells in females and is essential for gamete maturation
What is the role of kisspeptin in puberty?
GnRH release is thought to occur in response to the release of kisspeptin and neurokinin
These two factors are essential for the initiation of gonadotrophin secretion, and without them puberty will not occur
Activating mutations in these factors may also result in precocious puberty.
Loss of function and mutation in GPR54 gene causes a failure to progress through puberty in men due to Hypogonadotropic hypogonadism
Kisspeptin is a ligand for the G protein coupled receptor GPR54 which is expressed in hypothalamic GnRH neurons
Kisspeptin-GPR54 is essential for the initiation of the gonadotropin secretion at puberty
What is precocious puberty
onset of secondary sexual characteristics before 8 in girls and 9 in boys
what is delayed puberty
absence of secondary sexual characteristics by 13 in girls and 14 in boys
What is true precocious puberty
the entire HPG axis is activated, indicated by pulsatile GnRH release
This has a relatively high incidence, and is much more common in females
The majority of cases of true precocious puberty are idiopathic in females, however in males it is generally a key indication of some form of brain tumour
precocious pseudopuberty
the events are GnRH independent (not in hypothalamus)
This will generally occur due to increased androgen secretion, most commonly as a result of CAH. However, it may be due to a gonadotrophin secreting tumour
Many tumours will secrete hCG, which will act at LH receptors to stimulate the gonads resulting in sex hormone action
How do you differentiate between true precocious puberty and precocious pseudopuberty?
distinguished by GnRH test
In true precocious puberty, stimulation with GnRH will increase LH and FSH to pubertal range, in an LH:FSH ratio >1
In precocious pseudopuberty, stimulation with GnRH will only increase LH and FSH to prepubertal levels, in an LH:FSH <1
what is the definition of sex
Biological and refers to primary and secondary sexual characteristics
Is determined by chromosomes, genes and hormones and can be changed (transgender)
what is the definition of gender
psychological, social entity that is subjective to cultural norms
Is probably instilled from a young age by society
what is CAH (congenital adrenal hyperplasia)
block in adrenal steroidogensis affecting glucocorticoid synthesis
21-hydroxylase deficiency is most common cause - block in mineralocorticoid production so no cortisol or aldosterone
results in life threatening crisis due to adrenal crisis due to lack of salt production and blood pressure regulation
17OHP is the marker steroid which increases in CAH as it occurs before the block
male hormones can still be made so females are virilised to 46 XX DSD - male genetalia
females are more likely to survive as unusual genitals are recognised at birth, but not in males so they die of adrenal crisis