Lecture 26: Puberty Flashcards
What are the characteristics of “Normal” puberty and when are the 3 puberties and why is there is a stop in the middle
Normal puberty has progressive sequential changes over 3-4 years, due to central activation of the H-P-Gonadal axis
1st puberty is in fetus when virilising the genitalia - LH,FSH as high as adult
2nd is mini puberty 3 mo PP where masculinisation of the brain and phallus size increases (40% of adult)
Gap in childhood where puberty is actively held off, allowing bone growth before epiphyseal plate closure
3rd is beginning of adolescence- strong increase back to adult levels which is maintained
What is the timings for pubertal onset and sequence in girls
- Starts at 9.5-10 yrs old onset of breast development: tanner stage 2.
- Rapid growth then 2 years later is Menarche
- 1 more year of growth then stop
What is the timings for pubertal onset and sequence in boys
- Start at 11.5-12 yrs: Increased testicular enlargement - >3mL on orchidometer.
- Stage 2 pubic hair at 6 mo after
- Growth spurt start at 13 and continues longer until 17/18.
What is thelarche, pubarche
The onset of Breast development, pubic hair development
When does phallus length increase
Starts increasing from 12- 19, in childhood it stays the same size after mini puberty
What are 5 tanner stages of breast development starting from stage 2 (stage 1 is no breast development )
- Just visible breast bud with elevation of breasts and papilla- Slight firm, not fatty tissue as in obesity
- further elevation and areolar but no separation of contours
4, Areolar lifts off the breast
- Areolar goes back to the contour of the breast
What part of the hypothalamus contains the GnRH neurons that go to ant pit gonadotrophs
Median preoptic nucleus of the hypothalamus
Where is most of the sex steroid synthesis done in the female
Theca cells (stim by LH) use cholesterol to make testosterone which is aromatised in the Granulosa cell into Estradiol
What cell makes up the majority of the testes: sertoli or leydig
Sertoli cells in the seminiferous tubule. - Growth of these causes most of teste growth and development. (they produce inhibin)
How does LH and FSH release change throughout puberty
- Early: its tonic phase increases and night pulses begin
- Mid: Greater increase in tonic phase and higher amplitude night pulses
- Day and night pulses which continue onto adulthood
How is puberty actively switched off in childhood and what clinical implication does that have
Gonadostat: intrinsic CNS inhibitory mechanism which increases sensitivity to negative feedback from sex steroids.
GABA is a potent inhibitor of the pulsatile GnRH secretion necessary for puberty. GABA is made from glutamate by GAD found in the median basal eminence (hypothalamus)
where GnRH neurons are
Children with brain damage, epilepsy, cp, can go into puberty earlier
What is the trigger for the transition from childhood to puberty
Kisspeptin (made from KISS1 gene) released by neurons that project into the preoptic nucleus acts on GPR54 which regulates GnRH secretion/release from the hypothalamus.
What is a measure of sertoli cell function in boys
Negative feedback to FSH secretion - Inhibin produced by sertoli cells
What is Adrenarche, when does it occur and how does it relate to puberty- what signs does it cause
Adrenarche is the increase in adrenal androgen (DHEAS) production which occurs in late childhood from bone/chronological age of 8-10yrs. (trigger unknown)
This is a temporal association with puberty but Not a sign of puberty
- Induces pubarche, adult body odour, acne, oily skin
Not related to glucocorticoid/mineralocorticoid conc.
What is Leptin and how does it relate to puberty- what signs does it cause
Leptin is an adipostatic hormone. The amount of leptin increases with fat mass.
It may be a faciliatory signal to influence the timing of puberty as obese children have an earlier onset of puberty,, leptin peaks prior to onset of puberty etc.
What is the main factor that can control the timing of menarche
Weight gain lowers the age of menarche - body fatness. There is also variation between african americans and caucasian populations
How does the body composition - fat v lean v skeletal mass- change for males and females in puberty compared to relatively same composition in childhood
- Male have 1.5x more lean and skeletal mass than Females
- Females have 2x more fat mass than males. Male distribution is truncal while females is more generalised
For both there is increased bone mineral density in puberty with peak bone mass achieved in early 20s
Between what ages is Precocious puberty for male and female, what are the test done/definable features
First signs of puberty <8yo in girls, <9 yo in boys. With girls this is associated with a growth spurt but with boys this comes later.
The puberty must be progressive to show the HPG axis is switched on.
Test for recordable LH and FSH (E2 insensitive)
GnRH stimulation test: in puberty there is a large increase in LH
MRI for hamartoma, CNS tumour
What are the pathologies that can underlie precocious puberty and what is the likelihood for boys vs girls
- Neurological problems/brain injury: epilepsy, cp
- Hypothalamic hamartoma: collection of disorganised tissue-> gelastic seizures- eerie laughing
- CNS tumour (less common)
Pathology more common in boys and the younger the child is
What is the treatment for precocious puberty and why
Long acting GnRH agonist which shuts down the GnRH axis by stopping pulsatile secretion - therefore stopping progression of puberty.
- This is to preserve final height and for social indications - management of periods etc.
What are the differential diagnoses of early breast development - eg. Tanner stage 2
Due to exposure to E2 so not necessarily puberty
- True central puberty: progressive growth acceleration, bone age advancement
- Benign Premature Thelarche: slight turning on of the axis but stop, so non progressive with minimal growth acceleration/bone age advancement
- watch carefully but reassure
- Peripheral estrogen source: ovarian cyst (which when goes away get a withdrawal bleed) or tumour
- Exogenous estrogen: HRT, lavender, tea tree oil, COCP
What are the differential diagnoses of premature pubarche for girls v boys
All due to exposure to androgens
- In girls or boys: premature adrenarche: increased DHEAS without breast development/ tests <3mL
If testes more than 3mL then it is true puberty. Testosterone should be elevated as well not DHEAS
Other causes are
- abnormal secretion for adrenal tumour or mild congenital adrenal hyperplasia.
- Exogenous androgen medications, body building drugs.
What is the age range for Late puberty for girls and boys and what are the 3 differential diagnoses
Delayed puberty in >13 yo girls, 14 yo boys
- usually exaggerated constitutional delay of growth and development which is normal
- Hypogonadotrophic hypogonadism:
- Pituitary damage (eg. surgical) or malformation,
- Kallmann syndrome - x linked GnRH deficiency: so there is low LH and FSH, associated with anosmia. - Primary hypogonadism
- Turners syndrome: 46OX, Klinefelter syndrome 47XXY
LH and FSH will be high bc the axis is on but the gonads are not able to respond
