Puberty Flashcards
HPG axis is active when?
In fetal development
Continues to fxn in infancy “mini puberty”
(after infancy, axis enters quiescent state, referred to as juvenile pause)
What is HPG axis?
g
After infancy, HPG axis enters quiescent state, referred to as ________
juvenile pause
Gonadarche
pubertal onset started by RE-EMERGENCE of Hypothalamic GnRH secretion –>
Stim gonadotropins to secrete LH + FSH –>
bind receptors in ovaries/testes –>
gonadal maturation and the production of sex steroids.
Prepuberty vs puberty lvls of FSH
Prepuberty: FSH > LH
Puberty:
LH>FSH
- early puberty may not be very helpful
- pulses and peaks are happening at night, so measuring lvls during day may be no good
Lab evidence of puberty?
Serum sample of LH/FSH (during night)
or
Look at response of LH to a GnRH analog
- LH lvls >5-6 with pubertal response
Estrogen stimulated changes in girls (6)
- Breast development
- Genital growth (labia minora)
- Maturation of vaginal mucosa
- Uterine/endometrial growth
- Body compo changes (fat distribution more in hip)
- Menarche (E + prog)
Physical changes of Gonadarche in boys
- Enlargement of testes #1 way to tell
- mediated by gonadotropins (FSH + LH)
_________
everything else is caused by androgens (T or DHEA-S, androstenedione) - Scrotal changes
- Sexual hair
- Penile growth
- Prostatic/seminal vesicle growth
- Deepening of voice
- Increase in muscle mass
In both boys and girls, gonarche induces linear growth acceleration and bone age advancement. What is Bone age advancement mediated by?
Estrogen in both boys and girls
T is converted to E by aromatase in boys
What causes pubarche in both boys and girls?
Pubarche: pysical signs of pubic hair, axillary hair, body odor, and acne.
Increased production of adrenal androgens (DHEA-S, androstenedione)
Timing of puberty in girls
- Attainment of Tanner 2 breast development
- Menarche
Attainment of Tanner 2 breast development
- mean: 10.4
Menarche:
- mean 12.5 yrs
Timing of puberty in boys Testes > 3 ml Pubic hair Penile enlargement Peak heigh velocity
Testes > 3 ml: 11.8 (9-14) yrs
Pubic hair: 12
Penile enlargement: 13
Peak heigh velocity: 14
Delayed puberty in boys and girls
no puberty signs by Boys: 14 yrs
Girls: 13 yrs
or lack of progression
Girls: No menarche by 4 yrs after puberty starts
Boys: No completion of genital growth after 5 yrs
Bone age is really physiologic age
Onset of puberty is commensurate with child's biologic age (bone age) Boys start puberty at bone age of: 11.5-12 yrs Girls start puberty at bone age of: 10.5-11 yrs
Delayed puberty is due to?
Low gonadotropins
- HYPOgonadotropic (central) hypogonadism
Elevated gonadotropins
- HYPERgonadotropic (primary) hypogonadism
Constitutional growth delay
late bloomers
Grows nl --> falls to lower % --> grows at that percentage --> Puberty --> jumps back up to original % --> Reaches full growth potential
How to diff betwn late bloomer and indiv w/ hypogonadotropic hypogonadism?
- Bone age
ie: boy whos 15, and bone age is 13, and no pubertal signs: HH - Adrenarchy
ie: absence of adrenarchy: late bloomer
ie: adrenarche
15 y/o w. bone age of 15, small testes: HH - Body habitus
ie: late bloomers are typically thin
Congenital causes of HYPOgonadotropic hypogonadism
- Part of multiple hormone deficiencies: septo-optic dysplasia
- Genetic syndrome: Prader willi syndrome
Idiopathic hypogonadotropic hypogonadism (IHH)
isolated defect in GnRH or gonadotropins in the absence of any structural abnormalities of the hypothalamus or pituitary
Kallman syndrome(579)
- Causes
- Presentation
- Failure of complete puberty
- a form of hypogonadotropic hypogonadism - Defective migration of GnRH cells
- Defective formation of olfactory bulbs
Presentation:
- Low lvls of: GnRH, FSH, LH, T
- Infertility
- Ammenorrhea
Acquired causes of Hypogonadotropic hypogonadism
- Pituitary or hypothalamic tumor
- Cranial irradiation
- CNS infxn
- Infiltrative diseases
- histiocytosis, granulomatous disease, hemachromatosis - Autoimmune hypophysitis
