Physiology of Puberty Flashcards
Puberty:
- stage of physical maturation in
which an individual becomes
physiologically capable of pro-
creation - transition from childhood to
reproductive maturity
Onset of Puberty:
- 8-13 in girls
- 9-14 in boys
Physical changes in puberty:
- growth spurt
- secondary sex characteristics:
pubic & axillary hair, breasts, male
voice changes - menarche/spermatogenesis
What are growth spurts?
short periods of time when child experiences quick physical growth in height and weight
Growth Spurt: Signs:
- increased appetite: child’s
nutritional needs increase before
and during growth spurt - increase in bone and muscle
growth - increase in amount of fat stored in
the body
Chronological Order of Puberty: Girls:
- growth spurt
- thelarche: breast development
- pubarche: pubic hair
- adrenarche: axillary hair
- menarche: menstruation
*not always true
Chronological Order of Puberty: Boys:
- testicular enlargement
- penile length increases
- pubic hair
- growth spurt
- axillary and facial hair
- deep voice
Which scale is used to describe the onset and progression of pubertal changes?
The Tanner Stages
Tanner Stages: Difference between how girls and boys are rated?
- boys are rated for genital
development and pubic hair
growth - girls are rated for breast
development and pubic hair
growth
Tanner Stages: Girl’s Breast Development:
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Tanner Stages of Male External Genitalia:
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Tanner Stages: Pubic Hair Growth:
What is minipuberty?
- HPG axis is active in utero
- and first six months in boys
- first 2 years in girls
- **quiescent until the onset of
puberty
HPG Axis:
- at onset of puberty
- hypothalamus starts to produce
pulsatile secretion of
gonadotrophin-releasing hormone
(GnRH) - stimulates the pulsatile release of
FSH and LH from the anterior
pituitary
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Role of Hormones in HPG Axis:
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Role of Testosterone in Puberty:
- increased muscle mass
- penile growth
- deepened voice
- pubic hair growth
Role of LH in Puberty:
- stimulates testosterone production
- from interstitial cells of testes
Role of FSH in Puberty:
- stimulates testicular growth
- enhances production of an
androgen-binding protein - by Sertoli cells, which are a
component of the testicular tubule
necessary for sustaining sperm cell
maturation
Puberty: Extra-Gonadal Hormonal Changes:
- increased adrenal steroid
(androgen) from adrenal cortex - involved in secondary sexual
characteristics and growth of sex
accessory structures eg prostate - increased GH secretion from
anterior pituitary increases
elevation of insulin like growth
factor -> increased growth - increased TSH secretion from
anterior pituitary in both sexes - increases metabolic rate and
promotes tissue growth
What categories of factors affect the timing of puberty?
- genetic
- environmental
- neuroendocrine
What environmental factors can affect the timing of puberty?
- nutritional status
- chronic illness
- migration
- frequent infectious disease
- pollution
Timing of Puberty: Neuroendocrine Factors:
- neuroregulation of puberty vis
neuropetides: kisspeptin,
neurokinin B and dynorphin A - at onset of puberty, stimulatory
drive of neurokinin B increases - results in kisspeptin production
- which regulates GnRH hormones
Precocious Puberty: Ages:
- girls: <8yrs
- boys: <9 yrs
Delayed Puberty: Ages:
- girls: >13 yrs
- boys: >14 yrs
Precocious Puberty:
- early/premature puberty
- presence of true pubertal features
at a young and inappropriate age - either central/true precocious
puberty or peripheral/pseudo-
precocious puberty
Central/True Precocious Puberty:
- overview (3)
- causes (4)
- gonadotrophin dependent
- under 8 in girls, under 8 in boys
- premature activation of HPG axis
Causes:
- brain tumours
- raised intracranial pressure
- CNS malformation
- mutations of the kisspeptin
receptor hence dysregulation of
GnRH neurones
Central Precocious Puberty: Characteristics:
- secondary sexual characteristics
develop too early but not true
puberty - premature thelarche
- premature adrenarche/pubarche
Peripheral Precocious Puberty:
- overview
- causes
- gonadotrophin independent
- girls <8yrs, boys <9yrs
Causes:
- ingestion of sex steroids
- hormone-producing tumours
(ovaries/testes)
- adrenal gland abnormalities ->
congenital adrenal hyperplasia
causing overproduction of sex
hormones
Precocious Puberty: Management:
- goals of managing precocious
puberty are to treat the underlying
cause and block
production/response of excess
hormones - refer to endocrinologist to prevent
complications - baseline measurement of
hormones: LH, FSH, Testosterone,
GnRH - follow up
Precocious Puberty: Treatment:
- GnRH agonists halt the physical
progress of puberty - produce initial increase in sex
hormones - continued non-pulsatile
stimulation - LH and FSG synthesis inhibited
- oestrogen and testosterone levels
decline - GnRH antagonist blocks the
gonadotrophin receptors in the
pituitary - inhibit LH and FSH release directly
- lacks the initial surge typical of
GnRH agonists - treatment helps in very young
children with central precocious
puberty
Delayed/Late Puberty: Overview:
- more common in boys than girls
- most are not pathological
- family history common
- girls: >13yrs
- boys: >14yrs
Delayed Puberty: Causes:
- chronic illness: kidney
disease***search - malnutrition -> eating
disorder/coeliac disease - problem with ovaries, testes,
thyroid, pituitary - genetic conditions: Turner
Syndrome, Klinefelter Syndrome
Delayed Puberty: Peripheral Defects:
- hypergonadotrophic
hypogonadism or primary
hypogonadism - disorder of abnormal gonadal
function with decreased
testosterone in males and
oestradiol in females -> delayed
sexual development
Peripheral Defects: Hypergonadotrophic hypogonadism/primary hypogonadism: Causes:
- turner’s syndrome
- post-malignancy
chemo/radiotherapy - surgery can cause gonadal failure
- polyglandular autoimmune
syndromes
Turner Syndrome:
- female only genetic disorder
- 1 in every 1 in 2000 babies
- only one normal X sex
chromosome not two - 45X (45 chromosomes instead of
46) - primary and secondary female sex
characteristics are not fully
developed - short stature, webbed neck, widely
spaced nipples, shield like thorax
Turner Syndrome: Treatment:
- growth and sex hormone
substitution
Turner Syndrome:
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Delayed Puberty: Central Defects:
- congenital hypogonadotrophic
hypogonadism - due to a problem with the pituitary
gland or hypothalamus - decreased LH and FSH
- hence gonad will not be able to
produce sex hormones
Causes:
- hypothalamic lesions can lead to
low GnRH
- rare genetic mutations inactivating
FSH/LH or their receptors
Delayed Puberty: Central Defects: Diagnosis:
- low gonadotrophin levels
- poor response to stimulation with
GnRH stimulation test
**test checks how well the
pituitary gland works - imaging can help
Delayed Puberty: Treatment Overview:
- treat underlying cause
- use meds short term to increase
hormone levels and trigger the
start of puberty - hormone replacement therapy
Klinefelter Syndrome:
- mostly boys and men
- normal puberty and find out only
in adulthood..delayed puberty is
possible - 47XXY
- karyotype shows extra
chromosome - learning difficulties
Teenagers:
- taller than expected
- long limbs
- broad hips
- poor muscle tone and slow muscle
growth
- reduced facial and body hair
- hair grows later than usual
- small penis and testicles
Klinefelter Syndrome:
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Klinefelter Syndrome: Treatment:
Testosterone Replacement Therapy
General Investigation for Children with Pubertal Issues:
- Bloods: LH, FSH, thyroid and
growth hormones -> provide
current situation not future - Thyroid stimulates production of
growth factors and GH production - physical examination will inform
about puberty status - children within the normal range
for height and development are
not likely to have a medical
problem - hand x-ray to determine likely
adult height - ultrasound or MRI to check for
tumours
In terms of chronological order of puberty in boys, what is the first change?
- pubic hair
- axillary hair
- breast development
- testicular enlargement
testicular enlargement
“Papilla is elevated above the level of the chest wall.”
As per Tanner stages of girls breast development:
- stage 1
- stage 2
- stage 3
- stage 4
Stage 1
Early or Precocious puberty in girls occur in ages less than:
- 8
- 9
- 10
- 11
8 years old
What is the chromosome number in Turner Syndrome?
- 46XY
- 45Y
- 45X
- 47XXY
- 45X
What chromosome number in Klinefelter Syndrome?
- 46XY
- 45Y
- 45X
- 47XXY
- 47XXY
