Male Gonad Physiology

Question 1

___ stimulates leydig cells in testes to make testosterone.

Answer 1

LH

Question 2

HPG (T) axis

Answer 2

hypothalmic gnrh –> anterior pituitary lh, fsh –> testosterone and inhibin in testes

Question 3

___ stimulates sertoli cells in testes to promote sperm development

Answer 3

FSH

Question 4

___ forms inhibin in testes which is a mode of negative feedback

Answer 4

FSH

Question 5

____ feedsback at the pituitary from the testes

Answer 5

inhibin

Question 6

____ feedsback at the pituitary and hypothalamus from the testes

Answer 6

testosterone

Question 7

____ syndrome results from low production of gnrh in parvi-cellular hypothalamic neurons due to failure of cell precursors to migrate to the hypothalamus

Answer 7

kallman’s

Question 8

GnRH is secreted into the ____ portal.

Answer 8

hypothalamo-hypophyseal

Question 9

T/F GnRH levels in serum are too low for detection

Answer 9

T

Question 10

Target of GnRH

Answer 10

gonadotrope cells in anterior pituitary

Question 11

Circadian output of GnRH is regulated by _____ which results in highest levels of GnRH when?

Answer 11

melatonin –> peak in morning (highest level of LH and testosterone as well)

Question 12

T/F stress and other similar changes may inhibit gonadtropin release

Answer 12

T

Question 13

Higher frequency pulsatile gnrh release favors ___ secretion

Answer 13

LH

Question 14

Excessively frequent pulsation/pathologic or continuous GnRH initially increases LH and FSH in a ____ effect but leads to GnRH receptor downregulation with resulting low LH/FSH. This can be mimicked by treatment with a GnRH agonist like ____

Answer 14

flare effect –> downregulation –> leuprolide

Question 15

The process by which GnRH binding sites increase during troughs of GnRH pulses is called______

Answer 15

self priming

Question 16

GnRH analog like leuprolide results in high/low LH

Answer 16

low

Question 17

T/F LH and FSH are stored in separate granules

Answer 17

T

Question 18

LH is metabolized by the ___

Answer 18

liver

Question 19

LH/FSH has a longer serum half life.

Answer 19

FSH = 2 hours vs 20 mins

Question 20

___ residues on FSH inhibit its metabolism

Answer 20

sialic acid

Question 21

negative feedback on FSH is mediated by ____

Answer 21

inhibin b

Question 22

negative feedback on lh is mediated by ____

Answer 22

testosterone

Question 23

in early fetal development _____ controls development of testes and wolffian ducts

Answer 23

placental hcg

Question 24

in late fetal development ____ controls testes development as fetal HPG axis matures

Answer 24

pituitary lh

Question 25

In infancy, the hypothalamus is very sensitive to ___ negative feedback.

Answer 25

steroid

Question 26

At what point in time do nocturnal FSH/LH pulses begin?

Answer 26

puberty

Question 27

Testosterone synthesis

Answer 27

LH --> receptor --> STAR protein transports cholesterol from mitochondria into lumen of cell --> side chain cleavage to form pregnenolone --> either to progesterone or to androstenedione to testosterone

Question 28

______ is the rate limiting step of steroid synthesis

Answer 28

transport of cholesterol out of mitochondria into cell lumen by steroidogenic acute regulatory protein (STAR)

Question 29

_______ creates a hydroxyl group at the 17 carbon and cleaves the sidechain in steroid production

Answer 29

17 hydroxylase

Question 30

The final step of steroid production involves ____ which removes a keto group to form testosterone.

Answer 30

17beta dehydrogenase

Question 31

___ converts pregnenolone to progesterone

Answer 31

3beta dehydrogenase

Question 32

T/F most testosterone is free in circulation.

Answer 32

F --> mostly bound to albumin or SHBG but 2% free for receptors

Question 33

_____ binds androgen receptor with greater affinity than testosterone

Answer 33

DHT

Question 34

What is the location of the androgen receptor?

Answer 34

nucleus

Question 35

androgens dislodge ____ from the androgen receptor during binding

Answer 35

hsp90

Question 36

___ is needed to stimulate sertoli cell function but ___ is the main regulator of spermatogenesis

Answer 36

fsh and testosterone

Question 37

testosterone enters sertoli cells bound to ____

Answer 37

androgen binding protein

Question 38

4 ways sertoli cells support spermatogenesis

Answer 38

create specialized microenvironment, expose germ cells to high levels of testosterone, coordinate maturation via gap junctions, and transport of differentiating germ cells toward lumen

Question 39

____ occurs when anti-sperm antibodies form as a response to breach of the btb

Answer 39

autoimmune orchitis --> destruction of contralateral testis

Question 40

Type Ad sperm stem cells do what?

Answer 40

undergo mitosis to maintain supply, line basal layer --> dark

Question 41

Type Ap sperm stem cells do what?

Answer 41

undergo mitosis to produce clonal population, linked by cytoplasmic bridges --> mature simultaneously

Question 42

What kind of sperm stem cells enter spermatogenesis and then spermiogenesis

Answer 42

Ap --> b

Question 43

___ undergo meiosis 1

Answer 43

primary spermatocytes

Question 44

____ undergo meiosis 2

Answer 44

secondary spermatocytes --> form spermatids

Question 45

____ undergo spermiogenesis

Answer 45

spermatids

Question 46

4 stages of spermiogenesis

Answer 46

golgi, cap, acrosome, maturation phases

Question 47

____ phase is when a spermatid developes polarity

Answer 47

golgi phase

Question 48

___ phase is when the spermatid nucleus condenses and forms a cap

Answer 48

cap phase

Question 49

___ phase is when the acrosome matures and a tail develops

Answer 49

acrosome phase

Question 50

____ phase is when excess spermatid is extruded into a residual body

Answer 50

maturation phase

Question 51

Identification of primary hypogonadism

Answer 51

infertility precedes testosterone deficiency//fsh is elevated

Question 52

Identification of secondary hypogonadism

Answer 52

same time infertility and testosterone deficiency // low fsh and lh

Question 53

1st trimester hypogonadism leads to ___ and ___

Answer 53

ambiguous genitalia and hypospadias

Question 54

2nd/3rd trimester hypogonadism leads to ___ and ___

Answer 54

micropenis and cryptorchidsm

Question 55

Eunuchoid body proportions result from hypogonadism in what stage of life?

Answer 55

childhood (also pubertal delay/absence, and gynecomastia)

Question 56

What are the associated hormone levels? normal men or obstruction

Answer 56

normal

Question 57

What are the associated hormone levels? isolated spermatogenic failure

Answer 57

high fsh

Question 58

What are the associated hormone levels? hypergonadotropic hypogonadism (aka testicular failure)

Answer 58

high fsh, high lh, low testosterone

Question 59

What are the associated hormone levels? hypogonadtropic hypogonadism

Answer 59

low/normal fsh and lh, low testosterone

Question 60

Most common cause of congenital primary hypogonadism

Answer 60

Klinefelter 47 xxy

Question 61

increased risk of testicular cancer

Answer 61

klinefelter

Question 62

Bell clapper deformity

Answer 62

malformation of processus vaginalis (acrquired hypogonadism)

Question 63

testicular torsion and mumps orchitis can result in ____

Answer 63

acquired primary hypogonadism

Question 64

When does gonadtropin therapy for secondary hypogonadism have best efficacy?

Answer 64

if onset of secondary hypogonadism occurred after puberty