3. Puberty Flashcards
what is the normal age of onset of puberty in males and females
females = 8-13 yrs males = 9-14 yrs
list the 4 stages of female dev and their approximate age of onset
- breast bud growth (TELARCHE): 8-11 yrs
- pubic hair growth (ADRENARCHE): 11-12 yrs
- growth spurt
- menstrual cycle (MENARCHE): <16 yrs
list the 5 stages of male dev.
- testicular volume increase
- genitalia size increase
- pubic hair growth
- spermatogenesis
- growth spurt
what measurement is used to assess puberty dev. and what characteristics does it look at in males and females
Tanner scale
- females: breast size + pubic hair growth
- males: testicular volume + pubic hair growth
which hormones are responsible for onset of puberty in males and females
- females: oestrogen and testosterone
- males: testosterone
describe the occurence of accelerated somatic growth in males and females during puberty, inc. hormones involved
Depends on GH and sex steroids:
- females: earlier and shorter
- males: later, longer and slightly faster
why is accelerated somatic growth faster in females than males
epiphyseal fusion (i.e. end of somatic growth) depends on oestrogen
describe the general hormonal changes seen in puberty
- gradual activation of GnRH - pulsatile release…
- increased frequency and amplitude of LH pulses…
- gonadotrophins stimulate secretion of oestrogens and androgens
+ extragonadal hormonal changes, e.g. increased IGF-1 and adrenal steroids
why is it important than GnRH release be pulsatile
if GnRH Rs continuously exposed to GnRH, they become desensitised… stop FSH and LH production… stops gonadal steroids production
what is the role of GHRH and GH in puberty
Mediate accelerated somatic growth:
- Hypothalamus releases GHRH…
- stimulates AP somatotropes to release GH…
- GH stimulates growth spurt:
- increased TSH
- increased IGF-1 (from liver)
- increased metabolic rate and tissue growth
- increased androgens (mineral retention in body to support bone and muscle growth)
describe the role of the HPG axis in puberty
Sexual development
- Hypothalamus releases GnRH (pulsatile release)…
- stimulates AP gonadotrophs to release LH and FSH:
- nocturnal pulsatile release pre-puberty (9-12 yrs)
- steady increase in release with puberty onset - stimulates androgen and oestrogen production from gonads
why is body mass one of the key factors in female onset of puberty, and what is the effect of significant weight loss on the reproductive cycle
- Leptin release from adipose tissue signals attainment of critical weight (47kg)
- Pulsatile release stimulates hypothalamic KISS neurones… GnRH release
- Significant weight loss causes cessation of reproductive cycle = SECONDARY AMENORRHEA
what is the effect of LH in males and females
- males: stimulates testes Leydig cells to produce testosterone from cholesterol
- females:
i) stimulates ovarian Theca cells to produce androgens and progesterone
ii) triggers ovulation
what is the effect of FSH in males and females
- males: stimulates Sertoli cells to increase spermatogenesis (provide nutrition and hormonal support to germ cells)
- females:
i) stimulates Granulosa cells to produce oestrogen and progesterone
ii) triggers ovulation
iii) inhibin secretion
what is the role of inhibin
negative feedback:
i. inhibits FSH release from AP
ii. small inhibitory effect on LH
