LM 2.2: Normal Puberty Flashcards
what is the HPG axis?
GnRH neurons in the hypothalamus release GnRH
GnRH goes to the anterior pituitary which then releases LH and FSH
LH and FSH go to the testes and ovaries to produce sex serious and gametogenesis
estradiole and testosterone then exert negative feedback to the hypothalamus to reduce the amount of LH and FSH that the pituitary releases to keep circulating sex steroid levels stable
if you patient has a testosterone secreting tumor, what would LH and testosterone levels be?
low LH
high testosterone
if you rpaitents lack GnRH neurons in the hypothalamus, what would LH and estrogen levels be?
both would be low
if you patient has a defective androgen receptor, what would LH and testosterone levels be?
high LH and high testosterone
if you patient has hyperprolactinemia, what would LH and testosterone levels be?
low LH and testosterone
if you patient has been exposed to exogenous androgens, what would LH and testosterone levels be?
low LH and high testosterone
if you patient is anorexic what would LH and estrogen levels be?
low LH and low estrogen because GnRH neuron function would be decreased
if you patient has a 21-hydroxylase deficiency, what would LH and testosterone levels be?
low LH
high testosterone
if you patient has gonadal dysgenesis, what would LH and testosterone levels be?
high LH and low T
if your patient has sustained damage to her pituitary gland what would LH and estrogen levels be?
low LH and low E
if your patient has streak ovaries what would LH and estrogen levels be?
high LH and low estrogen
if you patient has an ovarian tumor that secretes estrogens what would your lH and estrogen levels be?
low LH and high estrogen
what are GnRH levels like pre-puberty?
the rise in sex steroids at puberty involves a re-awakening of the reproductive axis after a period of suppression
while GnRH continues to be released in pulses during childhood, these pulses are low and slow, possibly due to inhibition by estradiol produced in the brain
what happens to GnRH levels at puberty in a girl?
in early puberty, levels of GnRH and the speed and size of pulses increase, particularly at night
eventually, the GnRH pulses are consistent thoughout the day and settle into a regular, adult pattern
rising LH levels initiate gametogenesis and drive the release of sex steroids from the gonads
these hormones lead to the development of secondary sex characteristics
what is tanner staging?
pubertal progression is measured using Tanner staging
a Tanner stage is assigned independently to genitalia, pubic hair, and breast
what is Tanner stage 1?
both girls and boys have no sexual hair and flat-appearing chest with a raised nipple
what is Tanner stage 2?
a small, countable number of pubic hairs are present, testicular enlargement begins in boys, and a breast bud forms in girls
what is Tanner stage 3?
pubic hair coarsens, boys exhibit in increase in penile size and length, and in girls the breast mound forms
what is Tanner stage 4?
coarse hair is found across the pubis. The penis width and glands increases, and the breast enlarges, showing a raised, mounded areola
what is Tanner stage 5?
coarse hair is found both across the pubis and medial thigh, the penis and testes enlarge to adult size, and the breast has an adult contour with a now flattened areola
what is pubarche?
the appearance of pubic hair
what is thelarche
the start of breast development
what is diagnostic for delayed puberty in girls?
lack of thelarche at 13 years old
thelarche before the age of 8 indicates precocious puberty
aka the start of breast development
what is diagnostic for delayed puberty in boys?
testicular enlargement that does not start before 14 years old is diagnostic of delayed puberty
any sign of puberty before age 9 is precocious puberty in boys
which hormones drive growth during puberty?
growth prior to puberty is driven by thyroid hormone and growth hormone (GH)
the adolescent growth spurt is driven by GH and estrogens (both sexes)
18% of adult height is gained during puberty –> there is growth of both the trunk and the long bones of the limbs, although the latter occurs first, leading to temporarily reduced motor coordination
how does estrogen effect bone growth?
E2 initially promotes growth by acting on bone directly, causing the local release of insulin-like growth factor 1
estrogens and testosterone also increases GH secretion from the pituitary, leading to increased IGF-1 release from the liver into the circulation, which can act on bone
long term, high levels of sex steroids acting through the estrogen receptor cause growth to end by causing the closure of the epiphyseal growth plates
when do girls have peak growth? why?
the rate of growth peaks in girls around age 11, about 6 months prior to menarche
the increased production of estrogen at this time reaches a level that begins to cause epiphyseal closure
when do boys have peak growth? why?
peak height velocity occurs on average around age 13 in boys
if puberty does not occur, the long bones will continue to grow and the result will be eunuchoid proportions where a patient is both tall and has an arm span more than 2 cm greater than height
