Final Exam-- Hormones of Reproduction Flashcards
What are the three ways that “maleness” and “femaleness” can be characterized?
- Genetic sex (XX, XY)
- Gonadal sex (testis or ovaries)
- Phenotypic sex (genital sex– external genitalia)
What determines the Genetic sex?
sex chromosomes
- XX in females
- XY in males
How long are gonads indifferent/bipotential in the fetus?
through week 5
neither male or female
What week in fetus do testes begin to develop?
6-7 weeks
What week in the fetus do ovaries in females begin to develop?
week 9
T/F. Genetic sex always determines gonadal sex
FALSE– Genetic sex USUALLY determines gonadal sex
What features is gonadal sex determined by?
males–> testes
females–> ovaries
How many cell types do the gonads consists of?
three
What are the three cell types the Testes consists of?
- Germ cells
- Sertoli cells
- Leydig cells
What are the three cell types the Ovaries consists of?
- Germ cells
- Theca cells
- Theca + Granulosa cells
What cells in the testes produce spermatogonia?
Germ cells
What cells in the testes synthesize antimullerian hormone and inhibin?
Sertoli cells
What cells in the testes synthesize testosterone?
Leydig cells
What cells in the ovaries produce oogonia?
germ cells
What cells in the ovaries synthesize progesterone?
theca cells
What cells in the ovaries synthesize estrogen?
Theca + Granulosa cells
What hormones need to be present in order to create a male genital tract and external genitalia?
Antimullarian hormone (from Sertoli cells)
Testosterone (from Leydig cells)
What hormones need to be present in order to create a female genital tract and external genitalia?
it is the ABSENCE of antimullarian hormone and testosterone
What is phenotypica sex defined by?
physical characteristics of internal genital tract and external genitalia
What does the internal genital tract for males consist of? What about the external genitalia?
prostate, seminal vesicle, vas deferenes, epididymis
scrotum, penis
What does the internal genital tract for females consist of? What about the external genitalia?
uterine tubes, uterus, upper 1/3 of vagina
clitoris, labia majora, labia minora, lower 2/3 of vagina
What stimulates growth and differentiation of the Wolffian ducts in the fetus? What do they differentiate into?
testosterone
epididymis, vas deferens, seminal vesicles, and ejaculatory ducts
What causes atrophy of the mullerian ducts?
Antimullerian hormone
which would become female parts
What does growth and development of the external genitalia in the male during wks 9-10 depend on?
conversion of testosterone to dihydrotestosterone and androgen receptors
What aren’t the wolffian ducts stimulate in the female?
since the ovaries DO NOT produce testosterone
What are the ducts called that differentiate into the females parts? What parts of the internal female tract do they differentiate into?
Mullerian ducts–> into uterine tubes, upper 1/3 of vagine
What hormones are required for the female genitalia? What is required for growth of the structures to normal size?
NONE for them to differentiation
to normal size requires estrogen
What is it called when someone has a male genotype but a female phenotype?
Androgen Insensitivity Syndrome
When is Andorgen Insensitivity Syndrome discovered?
when a female at puberty shows breast development but no menstruation
What will a pelvic exam of someone with Androgen Insensitivity Syndrome show?
presence of testes and a short vagina
What is occur at the binding level of someone with Androgen Insensitivity Syndrome?
no binding of testosterone or dihydrotestosterone –> the androgen receptors absent/defective
What hormones will be elevated in someone with Androgen Insensitivity Syndrome?
elevated levels of testosterone and LH
due to neg. feedback suppression not being able to occur due to defective androgen receptors
What internal organs are absent in someone with Androgen Insensitivity Syndrome? What will they never have?
no uterine tubes, uterus, or upper vagina–> will never have menstrual cycles/pregnancy
What do the testes secrete in someone with Androgen Insensitivity Syndrome in utero? What does this cause?
both antimullerian hormone and testosterone
- suppression of mullerian ducts (hence no menstruation)
- but targets are unresponsive to testosterone–> therefore male genital tract and external genitalia failed to develop (female genitalia by default)
Why would someone with Androgen Insensitivity Syndrome have breast development?
due to high levels of LH stimulating testes producing estradiol from testosterone
estradiol promotes breast development
What is the Tx for someone with Androgen Insensitivity Syndrome?
removal of testes to prevent neoplasm after puberty (source of estrogen is now gone)
intermittent estrogen replacement therapy
What is the hormonal secretion driven by in both males and females?
hypothalamic-pituitary axis
What hormone is secreted beginning at week 4 of gestation?
What is secreted beginning b/w weeks 10-12?
GnRH
FSH/LH
Once FSH/LH are secreted b/w weeks 10-12 in utero; what happens to their levels?
they remain low until puberty
Before puberty, which hormone level is higher, FSH or LH? How does this change at during the adult reproductive period? What about in old age?
before puberty–> FSH > LH
at puberty–> LH>FSH
old age–> FSH>LH
When is FSH greater than LH in the female?
during childhood and elderly years
When is LH greater than FSH in females?
during puberty and reproductive years
What happens to FSH and LH levels during puberty?
they rise and become pulsatile (assoc. with female 28 day menstrual cycle)
What is the primary hormonal event that is initiated at puberty? What will this drive secretion of? What will that cause?
initiated of pulsatile secretion of GnRH –> which drives parallel secretion of FSH and LH –> therefore stimulate gonads to produce hormones
- testosterone in males
- estradiol in females
What is required for normal reproductive function?*
pulsatility
When do large pulses of LH occur during puberty?
nocturnal
What will GnRH up regulate? What will this cause?
its own anterior pituitary receptor
causes increase sensitivity of GnRH receptor in anterior pituitary
What drive secretion of FSH and LH?
GnRH
What is responsible for secondary sexual characteristics that appear during puberty?
increase circulating levels of sex steroids
What may delay onset of puberty?
Extreme stress or caloric deprivation
CNS and nutritional status may play a role
What effect will a decrease in melatonin have on onset of puberty?
it inhibits GnRH–> therefore a decrease in melatonin will cause an increase in GnRH–> causing puberty to occur earlier
When are melatonin levels highest in our life? when are they lowest?
highest–> during childhood and adulthood
lowest–> during puberty
What will removal of the pineal gland in a baby cause?
earlier onset of puberty (due to no melatonin produced to inhibit GnRH)
Do males or females tend to develop secondary sex characteristics sooner?
females
At what ages will we see the following in boys:
- pubic hair
- penile growth
- growth spurt
- 12-16 yrs
- 13-15 yrs
- 13-16 yrs
At what ages will we see the following in girls:
- breast development
- pubic hair
- menarche
- growth spurt
- 11-15 yrs
- 9-15 yrs
- 10-16 yrs
- 11-14 yrs
What will Leydig cell proliferation increase synthesis and secretion of?
testosterone
What is the growth of testes primarily due to? What does this initiate?
increase number of seminiferous tubules–> initiation of spermatogenesis
Does growth spurt and closure of epiphyseal plates begin and end earlier in males or females?
females
What does pubic/axillary hair growth proceed? What is it depend on?
proceeds menarche
dependent on increase secretion of adrenal androgens
What will activation of hypothalamic-pituitary axis in females drive? When is the first sign of budding of breasts?
synthesis of estradiol by ovaries
following w/in 2 years of menarche
What is the major androgenic hormone?
testosterone
The biochemical pathway for testosterone is similar to adrenal cortex, but what are the important differences?
- testes LACK 21 beta-hydroxylase and 11beta-hydroylase
2. testes HAVE additional enzyme 17beta-hydroxysteroid dehydrogenase
What additional enzyme do the testes have that the adrenal cortex does not? What does this enzyme do?
17beta-hydroxysteroid dehydrogenase
converts Androsternedione into Testosterone
What converts Testosterone into Dihydrotestosterone (DHT)? Where does this occur?
5alpha-reductase
at the target tissues
Is testosterone active in all androgenic target tissues?
no
at some tissues testoserone is converted into dihydrotestosterone by enzyme 5alpha-reductase
What percentage of circulating testosterone is bound to plasma proteins? What are those plasma proteins?
98%
Sex steroid-binding globulin (SSBG) and albumin
What form of circulating testosterone is biologically active?*
FREE
What functiosn as a reservoir for the circulating testosterone hormone?
SSBG (Sex steroid-binding globulin)
What is SSBG (Sex steroid-binding globulin) stimulated by? What is it inhibited by?
+ by estrogens
- by androgens (like neg. feedback)
What controls both functions of the testes?
Hypothalamic- pituitary axis (HPA)
Controls:
- FSH
- LH
What does FSH stimulate in the testes?
What does LH stimulate in the testes?
spermatogenesis and sertoli cell fxn
secretion of testosterone
What two negative feedback paths is HPA (Hypothalamic- pituitary axis) controlled by?
- testosterone INHIBITS both ant. pit. LH and hypothalamic GnRH secretion
- Sertoli cells secrete glycoprotein called INHIBIN –> that inhibits ant. pit. FSH secretion
What type of effect does testosterone have on the sertoli cells? Release of what is stimulated?
paracrine effect on them to stimulate release of inhibin
What is mediated by Testosterone?
- differentiation of epidiymis, vas deferens, seminal vesicles
- increase muscle mass
- pubertal growth spurt
- epiphyseal closure
- growth of penis and seminal vesicles
- deepening of voice
- spermatogenesis
- neg. feedback on Ant. Pit.
- libido
What is mediated by Dihydrotestosterone (DHT)?
- differentiation of penis, scrotum, and prostate
- male hair pattern
- sebaceous gland activity
- growth of prostate
What will the use of 5alpha-reductase inhibitors cause?
block conversion of testosterone to dihydrotestosterone
- block production of active androgens in some targets
Ex: finasteride–> used to Tx benign prostatic hyperplasia and male pattern baldness
What is used to Tx benign prostatic hyperplasia and male pattern baldness?
a 5alpha-reductase inhibitor called Finasteride
What will someone who lacks 5alpha-reductase result in, but has testes that secrete testosterone?
no dihydrotestosterone (DHT):
Therefore no:
- external male reproductive parts–> penis, scrotum, prostate
- in fetus; testes synthesized antimullerian hormone which suppressed mullerian ducts–> so no female reproductive tract; BUT had wolffian ducts differentiation and get internal male reproductive tract
