Lect 29: puberty Flashcards
Which sexual differentiation category depends on combination of sex chromosomes at time of conception
genetic sex
Which sexual differentiation category depends on development of testes or ovaries, presence of absence of Y chromosome
Gonadal sex
Which sexual differentiation category depends on apparant anatomic sex of individual
phenotypic sex
Sex determining Region of Y (SRY) produces what factor? when?
-
testis determining factor (TDF) which promotes testis differentiation
- females lack SRY gene, therefore their gonads do not recieve a signal for testicular formation
- during gestational weeks 6-7
testes secrete testosterone and Antimullerian hormone. What is the role of Antimullerian hormone
- degeneration of Mullerian ducts
- would have become female genital tract if not suppressed
function of testosterone on Wolffian ducts
- transforms Wolffian ducts into male reproductive tract
- epididymis, vas deferens, seminal vesicles and ejaculatory ducts
absence of mullerian inhibiting factor in females leads to
- development of mullerian ducts into female reproductive tract
in females, what happens to wolffian ducts in absence of testosterone
they degenerate
ovaries have what 3 cells types? function of each
- germ cells: oogonia
- granulosa cells: estradiol
- theca cels: androgens and progesterone
Function of Dihydrotesterone around gestational week 9-10
- stimulates differentiation of the external genitalia
- without it, female-like external genitalia develop
are hormones needed to cause development of female gonads or development of external genitalia?
- No, the development of female reproductive organs does not require hormonal products
- in females the mullerian ducts do not regress and give rise to fallopian tubes, uterus and vagina
- growth to normal size of external genitalia does depend on estradiol
What gene contributes to the development of the Mullerian duct
Wnt gene
which sexual differentiation, male or female, is hormone dependent
- male
- depends on antimullerian hormone (AMH) to suppress development of mullerian duct
Explain what is going on in Androgen insensitivity syndrome (aka undervirilzed XY)
-
no functional androgen receptor
- individuals are XY
- testes develop
- secrete AMH and testosterone
- both wolffian and mullerian duct regress
- female external genitalia develop -> blind ended vagina
- infertile
- classified as girl at birth
- diagnosed at puberty due to primary amenorrhea
What is the problem in individuals with congenital adrenal hyperplasia 21-hydroxylase deficiency (aka virilized XX)
- lack 21-hydroxylase enzyme involved in biosynthesis of aldosterone and cortisol
- lack of cortisol leads to excessive ACTH which results in hyperplasia of adrenal cortex and excessive adrenal androgens
congenital adrenal hyperplasia 21-hydroxylase deficiency (aka virilized XX) have what presentation
- individuals are XX: ovaries and internal genitalia
- female external genitalia develop but virilize
- enlarged clitoris to penile clitoris
- acne
- hirsutism
- labial folds can appear as empty scrotum as seen in cryptorchidism
- can leads to life-threatening adrenal insufficiency within first weeks of life
function of 21-hydroxylase
- involved in biosynthesis of steroid hormones aldosterone and cortisol
5a-reductase deficiency causes
- male pseudohemaphrotidism
- male internal genitalia with female-like external genitalia
XY with defective testes leads to
- no testosterone production
- no male or female internal genitalia
- female-like external genitalia
XY with defective AMH production or action leads to
- both male and female internal genitalia with male external genitalia
function of 5a-reductase
- testosterone -> dihydrotestosterone
puberty is characterized by maturation of
hypothalamic-pituitary-gonadal axis
start of male puberty is marked by
- increase in testicular size (gonadarche)
- followed by development of pubic hair and penile enlargement
sperm production and ejactulatory capability are developed around ages
13.5-13.7 years old
start of female puberty is marked by
-
thelarche: breast development
- mean age 10.9 yrs
what is important to know about the first few cycles of menstration after menarche
- non-ovulatory for first few cycles
- no positive feedback by estrogen
in girls, growth spurt (GH and IGF-1) begins in early puberty and is complete by
menarche
in boys, growth spurt (GH and IGF-1) begins when
near the end of puberty, almost 2 years later than girls
estrogen has what effect on bones during puberty
- fuse epiphyses (in both males and females)
- high levels may lead to shorter stature
- longer time to reach puberty in boys accounts for most of difference in stature
acne is a result of
- increase in sebaceous gland activity due to testosterone
adrenarche (adrenal androgen production) normally occurs around 8 yo in both sexes. function in females?
involved in secondary sex characteristics: pubic/axillary hair
what is responsible for pubertal timing
-
increase in pulsatile GnRH release
- first occurs during sleep: increases in LH release in both sexes that correlates with onset of early puberty
- this reverses in late puberty
major determinant of puberty timing
genetic; also percentage of body fat
signal for pubery: leptin theory
- a metabolic signal from adipose tissue may control onset of sexual maturation
- leptin
- protein product of obese gene
- plasma levels correlate with degree of adiposity and are regulated by fasting and feeding
- plays important role in regulation of body weight and metabolism
- leptin
signal for pubery: melatonin theory
- melatonin secreted from pineal gland
- synchronizes circadian rhythms with light/dark cycles
-
melatonin inhibits GnRH release
- puberty may be inititated by a reduction in melatonin secretion
- **removal of pineal gland precipitates puberty
pattern of gonadotropin levels through life of a female
- LH and FSH peak during fetal life and again in early infancy before falling to low levels throughout the rest of childhood
- at onset of puberty, LH and FSH levels slowly rise and then oscillate at regular monthly intervals
- menopause: LH and FSH rise to very high levels
what is the problem in gonadotropin-dependent precocious puberty
- increased gonadotropins: LH and FSH
- 5x more frequent in girls
- early pubic hair and menstruation
what is the problem in gonadotropin-independent precocious puberty
- normal gonadotropins, but increased gonadal hormones
- ex: testicular disorders, hCG secreting tumors, androgen secreting tumors, estrogen secreting tumors
treatment of gonadotropin-dependent precocious puberty
long-acting GnRH agonists
- results in initial release of FSH and LH, followed by down-regulation and desensitization of receptors -> reduced gonadotropins -> reduced sex steroids and biologic effects
tx of gonadotropin-independent precocious puberty
- surgical removal of tumor
what is hypogonadotropic hypogonadism? what is the syndrome called
- low gonadotropins result in low gonadal hormones
- deficiency of pulsatile release of gonadotropins -> delayed puberty
- Kallman’s syndrome
what is hypergonadotropic hypogonadism? what syndromes present with this
- low gonadal hormones result in high gonadotropins due to lack of negative feedback
- gonadal failure -> delayed puberty
- turner syndrome or Klinefelter’s syndrome
What is Kallman’s syndrome
- failure of fetal migration of GnRH neurons to hypothalamus
- hypogonadotropic hypogonadism
- gonadotropin deficiency
- see
- lack of pubertal development
- short stature
tx of Kallman’s syndrome
- supplemental sex steroid (estrogen or testosterone, later GnRH for reproductive capacity)
What is Turner’s syndrome
- XO
- female genital tract forms, no functional gonads, short stature, delayed or absent puberty, amenorrhea
- primary gonadal failure: hypergonadotropic hypogonadism
- absence of negative feedback
tx of Turner’s syndrome and Klinefelter’s syndrome
- GH first and then supplemental sex steroids
What is Klinefelter’s syndrome? what are complications that arise from it
- 47, XXY
- most common form of primary testicular failure: hypergonadotropic hypogonadism
- absence of negative feedback
- feminization
- complications: germ cell tumors, breast CA, osteoporosis
