Endocrine Day 3- Pregnancy and Male reprod. Flashcards
What happens to corpus luteum at end of menstural cycle in the absence of pregnancy?
CL degenerates and its produciton of progesterone and estraidol falls
What does the placenta produce during the beginning of preganncy?
HCG (human chorionic gonadotropin)
- This “rescues” the CL by acting on LH receptors on CL
- HCG has same beta subunit to LH and will act on LH receptors on CL
- CL will continue to produce progesterone until HCG levels fall at 9-12 weeks
Progesterone ____ pregnancy
maintains
Why does E/P continue to increase after HCG decreases?
- Placenta starts to make own E/P
- placenta makes estriol (major estrogen of pregnancy)
- Progesterone dominant until end of pregnancy
HCG levels are maintained until what week? Why?
- HCG levels maintained until week 9-12
- once placenta starts making own E/P, then HCG starts to fall
- Corpus luteum is then no longer maintained
What is the main estrogen of pregnancy?
Estriol
What is main estrogen of ovaries?
17-beta-estradiol
What is main estrogen of fat tissue?
Estrone
What is HCG?
- Secreted by trophoblast 7-9 days after ovulation
- responsible for maternal recognition of pregnancy
- same structure and function as LH
- Maintains CL
- Promotes estrogen and progesterone secretion from CL (CL is important in first 3 months)
- Stimulates testosterone production by the testes of male fetus
What triggers delivery process?
- Placental CRH stimulates fetal production of ACTH–> DHEA-S produced by fetus–> placenta where aromatase enzyme causes increase in local estrogen/progesterone ratio
- Increase in local prostaglandin (PGF-2 alpha)
- Increase in maternal oxytocin
- increase in maternal catecholamines
What stimulates secretion of labor hormones?
- Stretch receptors in cervix progject infor to anoxal projections in spinal cord
- cause increase in oxytocin from post pituitary
- increases prostaglandins from uterine wall
- causing increase in uterine contractions
oxytocin is major player in uterin contractions
What stimulates synthesis of breast milk?
Prolactin
What stimulates milk ejection?
Oxytocin
What acts on pre-pubertal femals breast to increase duct growth?
- Estrogen
- GH
- Adrenal steroids
What causes mammary gland development during pregnancy?
- Estrogen
- also acting on ant pituitary lactotrophs to increase enlargement/proliferation in preparation for breast feeding
- BUT high estrogen and progesterone block breast milk synthesis
-
Progesterone<– main one
- development of lobule-alveolar system
- prolactin
- GH
- adrenal steroids
What allows milk secretion?
- Once E/P levels diminish after delivery of placenta, then prolactin levels are allowed to increase and breast milk can be made
E and P ____ milk production
inhibit
____ causes growth of ductile system in breasts
____ causes development of lobular-alveolar system
Estrogen; progesterone
What is the funcitonal unit of the milk duct?
Alveoli
____ provides tonic inhibition of output of prolactin
dopamine
T/F, estrogen increases number and size of lactotrophs
true
also makes them more responsive to stimulatory factors
What does suckling of breast cause hormonally?
- Suckling of breast causes inhibition of dopamine from hypothalamus
- inhibiton of dopamine cause increase in prolactin levels to increase milk production
What hormonal effects does increased prolatin levels have?
- Increased PRL causes signal to increase dopamine (negative feedback to decrease further PRL output)
- Signals dopamine neurons to inhibit LHRH secretion
- this lowers LH/FSH/E/P and causes amenorrhea and state of infertility
- GnRH (LHRH) receive dopaminergic input from dopamein
- when dopamine active, inhibits LHRH, gonadotropin, E/P all in arcuate nucleus
What is relative response of prolactin levels initially after birth versus months out?
- Immediately after placenta birthed, prolactin levels allowed to increase and will increase rapidly with suckling episode
- Months later, level of PRL released with suckling decreases
- this allows LHRH neurons to escape dopamine inhibition and fertility is restored
Lenght of release of prolactin after birht is a ____ phenomenon
cultural
What is sheehan’s syndrome?
- Panhypopituitarism caused by major blood loss during birth
- major blood loss decreases flow to the ant pituitary
- Causes
- failure to lactate because of degnerated lactorophs
- loss of coritcotrops for ACTH, causes absence of pubic/axillary hair
- patient is amenorrheic d/t decrease LH/FSH
- Hypothyroidism
- Treatment
- admin end organ hormone (TH, E, P, coritcosteroids)
What does inhibin inhibit?
FSH
The male reproductive tract is a ____ feedback system only
negative
What is target of LH in the male?
Leydig cells
What do leydig cells produce?
Testosterone and some estradiol (both long loop negative feedback to hypothalamus and pit)
What is target of FSH?
Sertoli cells on seminiferous tubules to produce sperm
What 2 hormones work together to increase spematozoa?
FSH and Testosterone
What cells make inhibin?
Sertoli cells in seminiferous tubules
LH/FSH demonstrate what kind of rhythm in males?
LH= Circhoral
FSH inhibited by inhibin, so more flat release?
What does testosterone inhibit?
LH secretion (decreases secretion)
What does LH stimulation cause at the Leydig cells? (Cellular process specifically)
- LH binds causes G-protein second messenger to increase cAMP, increase protein kinase–> cholesterol–> testosterone
- testosterone easily diffuses out of cell because it’s a steroid hormone
What can testosterone be converted to in other tissues? What enzyme causes this?
Can be converted into DHT by 5 alpha reductase
also can be converted into estrogen by aromatse
How is testosterone carried in the blod?
mainly bound to proteins
Main 2 types of proteins:
- sex-steroid binding globulin
- albumin
How does testosterone act on various cells in body?
- Testosterone can diffuse into cell direcrtly and act to enlarge penile tissues and skeletal muscle
- Testosterone can be converted to DHT inside cells with 5-alpha reductase
- can cause prostate growth and hair loss
- Testosterone can also be converted to estrogen via aromatization
- fat cells in breast, brain have aromatase and can convert testosterone to estrogen
What comprises inhibin?
alpha, beta subunits
What comprises activin?
- Two beta subunits
- Activin sitmulates FSH secretion
What are major actions of testosterone?
- Fetal devleopment of
- epididymis
- vas deference
- seminal vesicles
- Pubertal growth of
- penis
- seminal vesicles
- musculature
- skeleton
- larynx
- spermatogensis
What is major action of DHT?
- Fetal development of
- penis
- penile urethra
- scrotum
- prostate
- pubertal growth of
- scortum
- prostate
- sexual hair
- sebaceous glands
- prostatic secretion
What is relative secretion of testosterone through lifespan?
- Peak in fetal T due to HCG and temporary fetal hypothalmus LHRH activation
- 2nd T peak necessary to stimulate testicular descent into scrotum
- decrease levels during childhood d/t increase GABA and decrase glutamate
- sharp rise in puberty–> adulthood
- decrease in adulthood d/t decrease tesosterone output by testes
- still adequate to produce sperm
What does early testosterone due to male fetus brain?
Lead to organize the brain into a “male” brian
Believed testosterone plays role in gender ID/preference
What is Kallmann syndrome? Symptoms? Treatments?
- Under virilization of male d/e failure of LHRH neurons to migrate from embylogical olfactory tissue into proper hypothalamic location
- lakc of adequate LH, FSH, testosterone production
- cannot produce sperm
- Symptoms
- decrease chest mass
- milk toast personlity
- patient will lack sense of smell as well (olfactory tissues not working correctly)
- Treatment
- testosterone
What can be used to treat precocious puberty in male/females?
LHRH super agonist
What is androgen insensntivity?
- Patient has XY genotype but does not have functional androgen receptors
- therefore, lack of virilization
- Symptoms:
- breast development
- less body hair
- increased fat deposition in hips/thighs
- mullerian inhibiting hormone (MIH) produced by presnce of Y chromosome causes elimination of development of internal female structure.
- blind-ending vaginal pouch
- tend to be taller because testosterone doesn’t close epiphyseal plates
- Treatmnet
- generally remove testes and then have to go on testosterone replacement
- can live as women if they want
What does HCG bind to in male fetus?
What does it stimulate?
What role does this substance have?
- HCG binds to leydig cells in male fetus (because HCG is like LH)
- Stimulates testosterone production in male fetus
- thought to play role in gender identification
What is secreted because of a Y genotype? What does it do?
Mullerian Inhibitng Hormone
- Inhibits production of female intrauterine organs
