Lecture 10: Repro Physiology Flashcards
The pulsatile action of which hormone initiates puberty?
GnRH
How does secretion of FSH vs. LH change from childhood vs. adult repro period vs. post-menopausal age?
- Childhood = FSH > LH
- Adult repro = LH > FSH
- Post-meno = FSH > LH
List functions of Sertoli Cells.
- Provide nutrients to developing spermatozoa
- Form tight junctions w/ eachother creating blood-testis barrier
- Secrete aqueous fluid into lumen of seminiferous tubule to help transport sperm into epididymis
Function of Leydig cells?
Synthesis and secretion of testosterone
Which enzyme found in the testes allows for conversion of androstenedione to testosterone?
17β-hydroxysteroid dehydrogenase
Which enzyme converts testosterone to DHT in the peripheral tissue?
5α-reductase
Which cell of the testes convert testosterone to estradiol, mediated by aromatase?
Sertoli Cells
Which hormone stimulates the conversion of cholesterol to pregnenolone and regulates the overall rate of T synthesis by the Leydig cell?
LH
Which hormone is responsible for closure of the epiphyseal plates?
Testosterone
List the specific actions of DHT both early and late in male life.
- Early = differentiation of penis, scrotum and prostate
- Late = prostate growth, male pattern balding, and sebaceous gland activity
Which class of drugs can be used as tx for BPH and hair loss in males?
5α-reductase inhibitors
How do sertoli cells provide negative feedback to the anterior pituitary gland?
Produce inhibin B —> inhibits FSH
Which hormone and cells of the testes are essential for formation of estrogens?
- FSH stimulates Sertoli cells
- Convert T –> estrogen via aromatase
What is the function of FSH and LH in spermatogenesis?
- FSH stimulates sertoli cells to nurse and form sperm
- LH stimulates leydig cells to secrete testosterone (needed for growth and division of testicular germ cells)
Which cells of the testes secrete androgen-binding protein necessary for maintaining local levels of testosterone?
Sertoli Cells
What is the underlying pathophysiology of Kallman syndrome and what is seen?
- Failure of GnRH migration into hypothalamus during embryonic development —> ↓ GnRH, FSH, LH, and Testosterone
- Characterized by delayed or absent puberty and impaired sense of smell
Which type of gonadotropic disorder is Kallman Syndrome?
Hypogonadotropic hypogonadism
What is Klinefelter syndrome due to, and what is seen with this disorder at birth and into adult life?
- Men born with extra X chromosome (barr body) and appear phenotypically normal at birth
- At puberty, ↑ levels of gonadotropins fail to induce normal testicular growth and spermatogenesis
- Seminiferous tubules are largely destroyed = infertility
What are levels of inhibin, FSH, testosterone, LH, and estrogen like in person with Klinefelter Syndrome?
- Dysgenesis of seminiferous tubulues –> ↓ inhibin B –> ↑ FSH
- Abnormal leydig cell function –> ↓ testosterone –> ↑ LH –> ↑ estrogen
- ↑ gonadotropins with ↓ testosterone = 1’ hypogonadism
What is the role of DHT in men with BPH?
- DHT is NOT ↑
- The BPH may be due to these pt’s having ↑ DHT receptors on their prostates
The follicular phase of the ovarian cycle coincides with which phase of the endometrial cycle?
Proliferative phase
Which hormone stimulates the granulosa cells to produce inhibins and what is the function of inhibins?
- FSH stimulates prod. of inhibins
- Just before ovulation granulosa cells acquire LH receptors, and LH also stimulates prod. of inhibin
- Inhibins inhibit FSH production
What is the major product of the follicle during the follicular phase?
Estradiol
What is the major product of the corpus luteum?
Progesterone
Which 3 hormones cause positive feedback on the HP axis inducing the LH surge seen w/ the menstrual cycle?
- Estrogen
- Progestins
- Activins
High levels of what hormone released in the late follicular phase ehances the sensitivity of the gonadotrophs to GnRH?
Estrogen
Which hormone promotes the differentiation of the stromal cells of the endometrium into predicdual cells, which must be prepared to form the decidua of pregnancy?
Progesterone
What are the levels of estrogen, inhibin, LH and FSH like during menopause?
- ↓ estrogen and ↓ inhibin
- No neg. feedback of LH and FSH; therefore ↑↑↑ LH and FSH
What are the levels of LH, FSH and testosterone like in patient with polycystic ovarian syndrome (PCOS)
- ↑ LH
- ↓ FSH
- ↑ Testosterone
Enlarged polycystic ovaries are associated with elevated levels of?
DHEA
What occurs during the acrosomal reaction of fertilization?
↑ in [Ca2+] inside sperm triggers fusion of the outer acrosomal membrane with the sperm cell’s plasma membrane –> exocytosis of the acrosomal contents
What is responsible for triggering the oocytes 2nd meiotic division and the cortical reaction?
↑ [Ca2+] inside the oocyte
What is the cortical reaction associated with fertilization and what is its function?
- Massive exocytosis of cortical granules seen shortly after sperm-oocyte fusion
- Granules contain enzymes that act on glycoproteins of zona pellucida and cause them to harden
- Prevents polyspermy
During which days of embryogenesis does the embryo reach the blastocyst stage?
Days 4-5
What initiates implantation?
Blastocyst coming in contact with uterine wall
Which cells are responsible for secreting proteases that digest the outer-lying zona pellucida allowing for the blastocyst to adhere to and implant into the receptive uterine endometrium?
Trophoblasts
List 4 functions of the Syncytiotrophoblasts following implantation
- Express cadherins and integrins for binding of embryo to uterus
- Secrete hCG which maintains viability of corpus luteum
- Make progesterone to maintain pregnancy independently of the corpus luteum
- Function in phagocytosis and bidirectional placental transfer of gases, nutrients and wastes
What is decidualization?
Response of maternal cells (stromal cells) to progesterone –> endometrial stroma transformed into enlarged and glycogen-filled decidual cells
What represents the functional unit of the placenta due to its branching greatly ↑ SA for maternal-fetal exchange?
Chorionic villi
What is the first hormone produced by the syncytiotrophoblasts and what receptor does it bind?
hCG which binds with HIGH affinity to the LH receptor
What is the primary function of the hCG secreted by syncytiotrophoblasts?
- Prevents luteolysis
and
- Maintains high levels of luteal-derived progesterone prod. during first 10 weeks
What is the function of human placental lactogen (hPL)?
- Antagonistic action to insulin —> diabetogenicity of pregnancy
- ↑ glucose availability by inhibiting maternal glucose uptake
- Lipolytic actions to help mother shift to the use of FFA’s for energy
Which hormone is produced in high amounts by the placenta and is required to maintain quiescent myometrium and a pregnant uterus?
Progesterone
Levels of what hormone can be used to assess fetal well-being?
Estriol
Which hormone increases the degree of uterine contractility and stimulates the synthesis of oxytocin receptors?
Estrogen
Which hormone is believed to initiate labor and plays a role in enhancing motility/contraction of uterine smooth muscle cells?
Prostaglandins
What is the function of oxytocin?
- Causes uterus to contract immediately after fetus is expelled
- Limits blood flow and blood loss
- ↑ uterine synthesis of prostaglandins
Prolactin levels ↑ 20 fold during pregnancy, but why is the action of prolactin inhibited?
Inhibition due to high estrogen and progesterone
What are levels of prolactin, estrogen, progesterone, GnRH, FSH, and LH like for the initiation of lactation?
- ↑ Prolactin
- ↓ estrogen and progesterone
- Neg. feedback –> ↓ GnRH —> ↓ FSH and LH
Which hormone enhances milk ejection by stimulating contraction of the network of myoepithelial cells surronding the alveoli and ducts of the breast?
Oxytocin
