LM 2.2: Normal Puberty

Question 1

what is the HPG axis?

Answer 1

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

Question 2

if you patient has a testosterone secreting tumor, what would LH and testosterone levels be?

Answer 2

low LH

high testosterone

Question 3

if you rpaitents lack GnRH neurons in the hypothalamus, what would LH and estrogen levels be?

Answer 3

both would be low

Question 4

if you patient has a defective androgen receptor, what would LH and testosterone levels be?

Answer 4

high LH and high testosterone

Question 5

if you patient has hyperprolactinemia, what would LH and testosterone levels be?

Answer 5

low LH and testosterone

Question 6

if you patient has been exposed to exogenous androgens, what would LH and testosterone levels be?

Answer 6

low LH and high testosterone

Question 7

if you patient is anorexic what would LH and estrogen levels be?

Answer 7

low LH and low estrogen because GnRH neuron function would be decreased

Question 8

if you patient has a 21-hydroxylase deficiency, what would LH and testosterone levels be?

Answer 8

low LH

high testosterone

Question 9

if you patient has gonadal dysgenesis, what would LH and testosterone levels be?

Answer 9

high LH and low T

Question 10

if your patient has sustained damage to her pituitary gland what would LH and estrogen levels be?

Answer 10

low LH and low E

Question 11

if your patient has streak ovaries what would LH and estrogen levels be?

Answer 11

high LH and low estrogen

Question 12

if you patient has an ovarian tumor that secretes estrogens what would your lH and estrogen levels be?

Answer 12

low LH and high estrogen

Question 13

what are GnRH levels like pre-puberty?

Answer 13

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

Question 14

what happens to GnRH levels at puberty in a girl?

Answer 14

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

Question 15

what is tanner staging?

Answer 15

pubertal progression is measured using Tanner staging

a Tanner stage is assigned independently to genitalia, pubic hair, and breast

Question 16

what is Tanner stage 1?

Answer 16

both girls and boys have no sexual hair and flat-appearing chest with a raised nipple

Question 17

what is Tanner stage 2?

Answer 17

a small, countable number of pubic hairs are present, testicular enlargement begins in boys, and a breast bud forms in girls

Question 18

what is Tanner stage 3?

Answer 18

pubic hair coarsens, boys exhibit in increase in penile size and length, and in girls the breast mound forms

Question 19

what is Tanner stage 4?

Answer 19

coarse hair is found across the pubis. The penis width and glands increases, and the breast enlarges, showing a raised, mounded areola

Question 20

what is Tanner stage 5?

Answer 20

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

Question 21

what is pubarche?

Answer 21

the appearance of pubic hair

Question 22

what is thelarche

Answer 22

the start of breast development

Question 23

what is diagnostic for delayed puberty in girls?

Answer 23

lack of thelarche at 13 years old

thelarche before the age of 8 indicates precocious puberty

aka the start of breast development

Question 24

what is diagnostic for delayed puberty in boys?

Answer 24

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

Question 25

which hormones drive growth during puberty?

Answer 25

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

Question 26

how does estrogen effect bone growth?

Answer 26

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

Question 27

when do girls have peak growth? why?

Answer 27

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

Question 28

when do boys have peak growth? why?

Answer 28

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