Physiology and regulation of puberty

Question 1

what s the definition of puberty

Answer 1

end of childhood to the achievement of sexual maturation and fertility
individuals undergo a period of physical and psychological changes

Question 2

what are the physical changes of puberty

Answer 2

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

Question 3

what are the psychological change of puberty

Answer 3

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

Question 4

what is puberty onset triggered by

Answer 4

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

Question 5

what is adrenarche

Answer 5

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

Question 6

what are physical signs of adrenarche

Answer 6

pubic/axillary hair development
axillary odour
acne

Question 7

what is gonadarche

Answer 7

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

Question 8

what are physical signs of gonadarche

Answer 8

breast development and growth of ovaries (oestradiol and progesterone production)
growth of testes (testosterone production)

Question 9

what is mini-puberty

Answer 9

transient postnatal HPG axis activation and sex steroid surge
influences reproductive organ development, body composition and growth, cognitive functions and behaviour

Question 10

what is thelarche

Answer 10

inset of female breast development (after 8yrs)
usually first sign of puberty in girls

Question 11

what is pubarche

Answer 11

development of pubic hair

Question 12

what is menarche

Answer 12

onset of menstruation
~2 years after thelarche

Question 13

what is spermarche

Answer 13

onset of sperm emission (first ejaculation)
coincides with development of secondary sex characteristics in mid-puberty

Question 14

describe what growth sput is and when is occurs

Answer 14

peak growth velocity in childhood after infancy
tanner stage 2-3 in girls (before menarche)
tanner stage 3-4 in boys

Question 15

describe tanner stage 1 in girls

Answer 15

breasts - elevation of papilla only
pubic hair - villus hair only
growth - 2-2.4 inches p/y
adrenarche and ovarian growth

Question 16

describe tanner stage 2 in girls

Answer 16

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

Question 17

describe tanner stage 3 in girls

Answer 17

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

Question 18

describe tanner stage 4 in girls

Answer 18

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

Question 19

describe tanner stage 5 in girls

Answer 19

breast - adult-type contour, projection of papilla only
pubic hair - adult hair, spreads to medial thigh
growth - cessation of linear growth
adult genetalia

Question 20

describe tanner stage 1 in boys

Answer 20

genitalia - testes <2.5cm
pubic hair - villus hair only
growth - 2-2.4 inches p/y
adrenarche

Question 21

describe tanner stage 2 in boys

Answer 21

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

Question 22

describe tanner stage 3 in boys

Answer 22

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

Question 23

describe tanner stage 4 in boys

Answer 23

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

Question 24

describe tanner stage 5 in boys

Answer 24

genitalia - testes >4.5cm, adult genitalia
pubic hair - adult hair spread to medial thighs
growth - deceleration, cessation
facial hair, muscle mass increases

Question 25

what is the function of hypothalamic kisspeptin

Answer 25

controlling pubertal onset
kisspeptin neurons and co-expressed neuropeptides, neurokinin B+ dynorphin, form a kisspeptin/neurokinin B/dynorphin A (KNDy) neuronal assemble

Question 26

what does KNDy do

Answer 26

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

Question 27

what may trigger increased GnRH release to initiate puberty

Answer 27

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

Question 28

what are the gentic factors that affect puberty

Answer 28

networks of functionally related, hierarchically arranged genes regulate the neuroendocrine control of puberty initiation
genetic explain 50-80% of variability in timing

Question 29

metabolic factors affecting puberty

Answer 29

leptin appears to play a permissive role in puberty initiation and maintenance of reproductive function

Question 30

what is precocious puberty

Answer 30

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

Question 31

what is delayed pubery

Answer 31

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

Question 32

what is contra-sexual development

Answer 32

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