B8.060 Prework: Puberty Flashcards
definition of puberty
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
tanner stages of breast development
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
tanner stages of pubic hair development
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
tenner stages of male genitalia
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
gonadal feedback regulation of LH and FSH
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
control of FSH secretion
inhibin and follistatin
produced by granulosa/sertoli cells
specifically inhibit FSH secretion with no effect on LH
act only on anterior pituitary
positive feedback of estrogen on HPG axis
preovulatory surges of LH and FSH are stimulated by E
E sensitizes the anterior pituitary to GnRH and also promoted hypothalamic release of GnRH
action of FSH
acts on granulosa cells of ovary and sertoli cells of testis
promote folliculogenesis and spermatogenesis respectively
action of LH
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
key functions of estrogens in puberty
- stimulate secondary sex characteristics
- mildly anabolic
- regulate behavior and secretion of gonadotropins
key functions of androgens in puberty
- induce body hair
- influence sexual behavior
- promote protein anabolism, somatic growth and ossification
what is a significant source of androgen production in females
adrenal cortex
what is adrenarche
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
changes that occur during puberty
- activation of cyclicity
- increase in sex steroid production by adrenal gland
- increases in circulating LH, FSH, and E
- final stage in the maturation of the HPO axis is the acquisition of the positive feedback effects of E on LH and FSH secretion
how are increases in circulating LH, FSH, and E achieved during puberty
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
what is the initiating event in midpuberty that starts gonadal development and steroidogenesis
nocturnal rise in GnRH > corresponding increase in LH
gonadal steroid independent changes in gonadotropin secretion following birth (hypothalamic level)
childhood:
strong GABAergic tone inhibits GnRH neurons
puberty:
increase in excitatory neurotransmitters (glutamate, NMDA, kisspeptin) begin to stimulate GnRH neurons more
maturational changes in E negative feedback to the hypothalamus
in children: super low levels of steroids can block gonadotropin release
with aging: more E required to inhibit gonadotropins
**gonadal steroid dependent changes
what occurs with puberty in girls
first ovulation, due to E2 positive feedback and LH surge
initiation of menstrual cycles
what is associated with sexual maturity
establishment of patterns (cyclicity) at the level of the hypothalamus, pituitary, ovary, and uterus
plus changes in phenotype and behavior
secondary sex characteristics
breast budding pubic hair growth spurt change in habitus menarche axillary hair adult breast
what factors can influence the timing of puberty (precocious or delayed?)
health nutrition stress (BMI) familial genetics environmental
causes of hypogonadotropic hypogonadism (secondary)
- CNS disorders
- tumors
- craniopharyngioma
- developmental defects - gonadotropin deficiency
- kallmanm syndrome
- pituitary defects
- misc (prader willi, anorexia, physical activity, hypothyroidism)
how can hypothyroid lead to delayed puberty
increased TRH > increased prolactin release > inhibition of GnRH
causes of hypergonadotropic hypogonadism (primary)
klinefelter
cryptorchism/anorchia
turner syndrome
chemotherapy/radiation
