B8.060 Prework: Puberty

Question 1

definition of puberty

Answer 1

period of becoming first capable of reproducing sexually
brought on by production of sex hormones and the maturing of the reproductive organs
development of secondary sex characteristics and first menstruation in females

Question 2

tanner stages of breast development

Answer 2

B1- preadolescent, elevation of papilla only
B2- breast bud, elevation of breast and papilla as small mound, enlargement of areola
B3- further enlargement of breast and areola with no separation of contours
B4- projection of areola and papilla to form a secondary mound above the level of the breast
B5- mature stage, projection of papilla onle, due to recession of areola to the general contour of the breast

Question 3

tanner stages of pubic hair development

Answer 3

P1- preadolescent, no pubic hair
P2- sparse, long, slightly pigmented, downy hair
P3- darker, courser, curlier
P4- hair is adult type, but area covered by it is smaller than in adults
P5- hair is adult in quantity and type, spreads to medial thigh

Question 4

tenner stages of male genitalia

Answer 4

G1- preadolescent, testes, scrotum, and penis are about the same size and proportions as in early childhood
G2- scrotum and testes have enlarged, there is a change in the texture and reddening of scrotal skin
G3- growth of penis has occurred, mainly in length but some increase in breadth; further growth of testes and scrotum
G4- penis further enlarges in length and girth with development of glans; testes and scrotum more enlarged; scrotal skin darkened
G5- genitalia is adult in size and shape

Question 5

gonadal feedback regulation of LH and FSH

Answer 5

steroid hormones produced in response to gonadotropin stimulation feedback at the level of the hypothalamus and the anterior pituitary to reduce gonadotropin secretion
effects of steroid hormones are more prominent on LH than FSH

Question 6

control of FSH secretion

Answer 6

inhibin and follistatin
produced by granulosa/sertoli cells
specifically inhibit FSH secretion with no effect on LH
act only on anterior pituitary

Question 7

positive feedback of estrogen on HPG axis

Answer 7

preovulatory surges of LH and FSH are stimulated by E

E sensitizes the anterior pituitary to GnRH and also promoted hypothalamic release of GnRH

Question 8

action of FSH

Answer 8

acts on granulosa cells of ovary and sertoli cells of testis

promote folliculogenesis and spermatogenesis respectively

Question 9

action of LH

Answer 9

acts on leydig cells of testis and theca cells of ovary to stimulate steroid production
also stimulates ovulation and formation and maintenance of corpus luteum

Question 10

key functions of estrogens in puberty

Answer 10

1. stimulate secondary sex characteristics
2. mildly anabolic
3. regulate behavior and secretion of gonadotropins

Question 11

key functions of androgens in puberty

Answer 11

1. induce body hair
2. influence sexual behavior
3. promote protein anabolism, somatic growth and ossification

Question 12

what is a significant source of androgen production in females

Answer 12

adrenal cortex

Question 13

what is adrenarche

Answer 13

increased adrenal androgen production (DHEA) prior to puberty > due to activation of the 17-20 desomolase enzyme
secondary sex characteristics develop
happens 2 years before puberty

Question 14

changes that occur during puberty

Answer 14

1. activation of cyclicity
2. increase in sex steroid production by adrenal gland
3. increases in circulating LH, FSH, and E
4. final stage in the maturation of the HPO axis is the acquisition of the positive feedback effects of E on LH and FSH secretion

Question 15

how are increases in circulating LH, FSH, and E achieved during puberty

Answer 15

achieved by a reduction in the sensitivity of the hypothalamus to the negative feedback effects of estrogen
frequency and amplitude of LH and FSH pulses result in a greater stimulation of the ovaries and greater production of E

Question 16

what is the initiating event in midpuberty that starts gonadal development and steroidogenesis

Answer 16

nocturnal rise in GnRH > corresponding increase in LH

Question 17

gonadal steroid independent changes in gonadotropin secretion following birth (hypothalamic level)

Answer 17

childhood:
strong GABAergic tone inhibits GnRH neurons
puberty:
increase in excitatory neurotransmitters (glutamate, NMDA, kisspeptin) begin to stimulate GnRH neurons more

Question 18

maturational changes in E negative feedback to the hypothalamus

Answer 18

in children: super low levels of steroids can block gonadotropin release
with aging: more E required to inhibit gonadotropins
**gonadal steroid dependent changes

Question 19

what occurs with puberty in girls

Answer 19

first ovulation, due to E2 positive feedback and LH surge

initiation of menstrual cycles

Question 20

what is associated with sexual maturity

Answer 20

establishment of patterns (cyclicity) at the level of the hypothalamus, pituitary, ovary, and uterus
plus changes in phenotype and behavior

Question 21

secondary sex characteristics

Answer 21

breast budding
pubic hair
growth spurt
change in habitus
menarche
axillary hair
adult breast

Question 22

what factors can influence the timing of puberty (precocious or delayed?)

Answer 22

health
nutrition
stress (BMI)
familial
genetics
environmental

Question 23

causes of hypogonadotropic hypogonadism (secondary)

Answer 23

1. CNS disorders
   - tumors
   - craniopharyngioma
   - developmental defects
2. gonadotropin deficiency
   - kallmanm syndrome
   - pituitary defects
   - misc (prader willi, anorexia, physical activity, hypothyroidism)

Question 24

how can hypothyroid lead to delayed puberty

Answer 24

increased TRH > increased prolactin release > inhibition of GnRH

Question 25

causes of hypergonadotropic hypogonadism (primary)

Answer 25

klinefelter
cryptorchism/anorchia
turner syndrome
chemotherapy/radiation