Physiology and regulation of puberty Flashcards
what s the definition of puberty
end of childhood to the achievement of sexual maturation and fertility
individuals undergo a period of physical and psychological changes
what are the physical changes of puberty
increase in body mass, height and stength
growth of central nervous system
brain development is complete
heart, lungs and viscera increase in size and mass
significant regression of lymphoid tissue
enlargement of reproductive organs
apocrine sweat glands are activated (associated with hair follicles in groin and axillary region)
development of pubic hair
what are the psychological change of puberty
activation of social and motivational tendencies
development of personality and sexual identity
abstract thinking
introspection
establishment of a system of values
autonomy and personal independence
development of coping strategies for overcoming problems and crises
focus and increased importance on peer relationships
what is puberty onset triggered by
activation of the HPG axis
complex neuroendocrine mechanisms activate this
there are global variations in timing of pubertal onset and tempo of normal puberty
influenced by genetic, metabolic and environmental factors
what is adrenarche
occurs ~2 years before puberty
prepubertal awakening of the adrenal gland
adrenal-androgen precursor secretion (DHEA, DHEA-S, androstenedione) which are then converted to sex steroids
what are physical signs of adrenarche
pubic/axillary hair development
axillary odour
acne
what is gonadarche
occurs at 8-14 years
increased pulsatile release of GnRH from the hypothalamus leads to increased pituitary release of LH and FSH
true central puberty
what are physical signs of gonadarche
breast development and growth of ovaries (oestradiol and progesterone production)
growth of testes (testosterone production)
what is mini-puberty
transient postnatal HPG axis activation and sex steroid surge
influences reproductive organ development, body composition and growth, cognitive functions and behaviour
what is thelarche
inset of female breast development (after 8yrs)
usually first sign of puberty in girls
what is pubarche
development of pubic hair
what is menarche
onset of menstruation
~2 years after thelarche
what is spermarche
onset of sperm emission (first ejaculation)
coincides with development of secondary sex characteristics in mid-puberty
describe what growth sput is and when is occurs
peak growth velocity in childhood after infancy
tanner stage 2-3 in girls (before menarche)
tanner stage 3-4 in boys
describe tanner stage 1 in girls
breasts - elevation of papilla only
pubic hair - villus hair only
growth - 2-2.4 inches p/y
adrenarche and ovarian growth
describe tanner stage 2 in girls
breast - breast bud under areola, areola enlargement
pubic hair - sparse hair along labia
growth - 2/8-3.2 inches p/y
clitoral enlargement, labia pigmentation, growth of uterus
describe tanner stage 3 in girls
breast - breast tissue grows, but has no contour or separation
pubic hair - coarser hair curled, pigmented covers the pubes
growth - 3.2 inches p/y
axillary hair, acne
describe tanner stage 4 in girls
breasts - projection of areola and papilla, secondary mound formation
pubic hair - adult hair, does not spread to thigh
growth - 2.8 inches p/y
menarche and development of menses
describe tanner stage 5 in girls
breast - adult-type contour, projection of papilla only
pubic hair - adult hair, spreads to medial thigh
growth - cessation of linear growth
adult genetalia
describe tanner stage 1 in boys
genitalia - testes <2.5cm
pubic hair - villus hair only
growth - 2-2.4 inches p/y
adrenarche
describe tanner stage 2 in boys
genitalia - testes 2.5-3.2 cm, thinning and reddening of scrotum
pubic hair - sparse hair at penis base
growth - 2-2.4 inches p/y
decreases in body fat
describe tanner stage 3 in boys
genitalia - testes 3.3-4cm, increase of penis length
pubic hair - thicker curlier hair spreads to pubis
growth - 2.8-3.2 inches p/y
gynaecomastia, voice break, increased muscle mass
describe tanner stage 4 in boys
genitalia - testes 4.1-4.5 cm, penis growth, darkening of scrotum
pubic hair - adult hair, does not spread to thighs
growth - 4 inches p/y
axillary hair, voice change, acne
describe tanner stage 5 in boys
genitalia - testes >4.5cm, adult genitalia
pubic hair - adult hair spread to medial thighs
growth - deceleration, cessation
facial hair, muscle mass increases
what is the function of hypothalamic kisspeptin
controlling pubertal onset
kisspeptin neurons and co-expressed neuropeptides, neurokinin B+ dynorphin, form a kisspeptin/neurokinin B/dynorphin A (KNDy) neuronal assemble
what does KNDy do
express kisspeptin and intermittently send stimulatory signals to GnRH neurons to generate a pulsatile GnRH secretion pattern
kisspeptin binds to the G-protein coupled receptor (KISS1R) expressed by GnRH neurons to initiate a sequence of downstream events
what may trigger increased GnRH release to initiate puberty
pubertal clock or somatometer
kisspeptin secretion is triggered, increased kisspeptin increases GnRH secretion
decreased melatonin reduces gonadotropin inhibiting hormone (GnIH)
increased leptin reduces inhibition of gonadotropins by GnIH
what are the gentic factors that affect puberty
networks of functionally related, hierarchically arranged genes regulate the neuroendocrine control of puberty initiation
genetic explain 50-80% of variability in timing
metabolic factors affecting puberty
leptin appears to play a permissive role in puberty initiation and maintenance of reproductive function
what is precocious puberty
early development of secondary sex characteristics (before 8 in girls and 9 in boys)
can be a variant of normal development or constitutional/idiopathic precocious puberty
other causes may be benign premature adrenarche, CNS or pituitary lesions, McCune-Albright syndrome
gonadotropin-secreting tumours or exogenous sex hormones
what is delayed pubery
absence or incomplete development of secondary sex characteristics (by 13 in girls and 14 in boys)
can be a variant of normal development or constitutional delay
other causes include hypogonadotropic hypogonadism, hypopituitarism, chromosomal abnormalities or hypothalamic dysfunction due to secondary causes
what is contra-sexual development
when male or female children develop physical features of the opposite genders
more prevalent in girls, commonly caused by polycystic ovaries, increased adrenal gland responses, or rarely other endocrine pathologies
less common in boys, typically caused by oestrogen-secreting tumours
