Puberty, Sexual Differentiation Flashcards
GnRH
- decapeptide (10aa)
- prod in arcuate nucleus
- pulsatile release
- neurons start in nose and migrate thru forebrain
GnRH secretion is governed by
kisspeptin
classification of sexual maturity
tanner classification
the HPO axis becomes quiescent
4-6 weeks after birth
adrenarche
6-8 yr
thelarche
breast development
10 yr
In the 5 years prior to puberty, gonadotropin levels are
low
very sensitive negative feedback system
leptin role in puberty
affects maturation of GnRH pulse generator
assoc w/ initiation of puberty
Kallman’s
adrenarche occurs despite absence of gonadarche
impaired migration of GnrH neurons to hypothalamus
Addison’s
gonadarche despite absence of adrenarche
Precocious puberty
gonadarche precede adrenarche
major determinant of timing of puberty
genetics
GnRH dependent causes of precocious puberty
- central nervous system tumors
- hypothalamic hamartoma
- craniopharyngiomata
- gliomata
- metastatic disease
- arachnoid or suprasellar cysts
- CNS infec/inflamm/injury
GnRH independent causes of precocious puberty
- exogenous sex steroid admin
- primary hypOthyroidism
- ovarian tumors
- simple ovarian cyst
- adrenal tumors
hypERgonadotripic hypOgonadism
gonadal dysgenesis (Turner’s syndrome)
hypOgonadotropic hypOgonadism
- constitutional delay
- kallmann
- anorexia, extreme exercise
- pituitary tumors
- hyperprolactinemia
- drug use
anatomic causes of delayed puberty
mullein agenesis
imperforate hymen
transverse vaginal septum
Kallmann Syndrome in Females
anosmia
amenorrhea
hypOplastic olfactory tracts
arcuate nucleus does NOT secrete GnRH
Kallmann Syndrome in Females
tx
steroid hormone replacement
Turner syndrome
45XO streak gonads absent follicles primary amenorrhea short stature webbed neck shield chest widely spaced nipples high arched palate
Marked LOF mutations of the 21-hydroxylase gene
congenital adrenal hyperplasia
21-hydroxylase –> cortisol prod
hyperkalemia, hypOtensive
complete androgen insensitivity syndrome
- external female, blind vaginal pouch
- no internal structures at all
5 alpha reductase deficiency
AR
46XY with ambiguity genitalia
internal male (undescended testes –> sertoli –> AMH –> mullein degen –> blind ending vagina
mixed gonadal dysgenesis
chromosomal abnormality causes a child to be born w/ 2 different gonads
2nd most comm cause ambiguous genitalia
most cases of MGD involve mosaicism (46XY, 45XO)
