Sexual Development and Reproductive Hormones

Question 1

When is genetic (chromosomal) sex determined?

Answer 1

At fertilization

Question 2

Gonadal sex is determined by what genes?

Answer 2

Testis determining (SRY and SOX9)

Ovary determining (RSPO1 and WNT)

Question 3

Hormones involved in determination of phenotypic sex

Answer 3

Anti-Mullerian
Testosterone
Dihydrotestosterone

Question 4

What happens in the presence of Testis Determining Factor (TDF) SRY?

Answer 4

Medullary cords differentiate into Sertoli cells, cortical sex cords degenerate

Sex cords differentiate into seminiferous tubules and give rise to rete testis

Pre-Sertoli cells produce Anti-Mullerian hormone

Question 5

What happens in the absence of SRY?

Answer 5

cortical sex cords develop into follicles, medullary sex cords degenerate. Makes a female.

Question 6

What occurs in bovines when fusion of placental circulation causes Anti Mullerian Hormone to transfer from a male to a female co-twin?

Answer 6

Free Martinism. Vestigial development of vagina, cervix, uterus and uterine tubes. Female can’t breed. Almost normal vulva and vestibulum.

Question 7

What disorder is caused by a disagreement between chromosomal and gonadal sex?

Answer 7

Sex reversal.

XX genotype but some testicular development.

XX male if bilateral testes

XX true hermaphrodite if testis and ovary present

Question 8

Why does sex reversal happen?

Answer 8

SRY translocation in most cases

20% have no SRY

Question 9

Functional areas of the female hypothalamus (2)

*secrete GnRH

Answer 9

Tonic - arcuate ventromedial region; ARC

Surge - preoptic area; POA - causes ovulation

Question 10

Role of testosterone in development of the hypothalamus

Answer 10

Inherently female. Testosterone crosses BBB and is converted to estradiol, which defeminizes brain and eliminates surge center.

*Estradiol from fetal ovaries is bound to alpha-fetoprotein and does not cross BBB

Question 11

Examples of body functions hormones regulate

Answer 11

Metabolism
Sleep
Lactation
Growth
Mood
Reproduction

Question 12

3 main classes of hormones

Answer 12

Steroids
Peptides/proteins/glycoproteins
Eicosanoids

Question 13

Endocrine hormones

Answer 13

Estradiol and FSH

Question 14

Neuroendocrine hormones

Answer 14

Gonadotropin Releasing Hormone (GnRH)

Question 15

Testosterone from Leydig cells influencing Sertoli cells in the testis is an example of what type of hormone delivery?

Answer 15

Paracrine

Question 16

Estradiol from Sertoli cells hastening development of these same cells is what type of hormone delivery?

Answer 16

Autocrine

Question 17

The “Ram Effect”, in which females all go into heat at the same time when a Ram is around, is an example of what kind of hormone delivery?

Answer 17

Pheromonal or “ectohormonal”

Question 18

Besides the Ram Effect, what’s another example of Pheromonal hormone delivery?

Answer 18

Bruce Effect - female mice terminate pregnancies due to pheromones of an unfamiliar male in the area.

Question 19

How does supraphysiological stimulation work?

Answer 19

Normally, hormone receptors are internalized as part of a negative feedback mechanism, which renders the hormone ineffective.

It is possible to overcome this mechanism with treatment. (Fertility treatments increase ovulation rates past what is physiologically normal)
*Supprelin = high dose GnRH analogue

Question 20

The pineal gland produces _____, which regulates cycles of seasonal breeders

Answer 20

Melatonin

Question 21

The pituitary gland produces which 4 hormones?

Answer 21

FSH
LH
Prolactin
Oxytocin

Question 22

The ovaries produce which 5 hormones?

Answer 22

Estradiol
Progesterone (by Corpus Luteum!)
Inhibin
Testosterone
Relaxin

Question 23

The testes produce which 3 hormones?

Answer 23

Testosterone
Inhibin
Estradiol

Question 24

Prostglandin F2 alpha (PGF2a) is produced by which organ?

Answer 24

Uterus

*also produces some estradiol

Question 25

Progesterone, estradiol, hCG, eCG, oxytocin, and PGF2a are produced by...

Answer 25

The placenta

Question 26

Estradiol, Progesterone, and Testosterone are what kind of hormone?

Answer 26

Steroids. *Can diffuse through skin/mucosa and cause prolonged effects.

Question 27

What type of hormone can be converted from one form to another based on what the body needs?

Answer 27

Prostaglandins (PGF2a <> PGE2)

Question 28

Steroid biosynthesis with treatment...

Answer 28

Can administer one form of a steroid and it changes to another. Estradiol administered to cattle would convert to testosterone. It's bad.

Question 29

Where is Estradiol produced and metabolized? What pathological effect can it have on males?

Answer 29

Produced mainly in follicular cells of ovaries * some in placenta * small amt in adrenals, testis, fat Metabolized in the liver Males with neoplastic conditions of the testes will have too much estradiol which will cause fertility issues

Question 30

Functions of Estradiol

Answer 30

``` Sexual behavior Uterine development/function Cervical mucous (indicator of cycle) Vaginal proliferation Mammary development Mediated ovulatory surge of LH Bone health/anabolic ```

Question 31

What enzyme is involved in the synthesis of endogenous estrogens from androgens?

Answer 31

aromatase

Question 32

Which cells of the corpus luteum produce progesterone?

Answer 32

Both granulosa (large luteal) and theca interna (small luteal cells). *Large luteal (granulosa) produce more

Question 33

Functions of progesterone

Answer 33

``` Development/function of uterus QUIESCENCE of myometrium Closure of cervix MAINTENANCE OF PREGNANCY Mammary development EFFECTS ON BRAIN effects on immune function ```

Question 34

5-a-Dihydroprogesterone, critical for equine pregnancy, is what type of hormone which binds to progesterone receptors?

Answer 34

progestagens

Question 35

Where is testosterone produced and metabolized?

Answer 35

Produced mainly by Leydig cells of testes Some in ovaries and adrenals Metabolized by liver and minorly in prostate

Question 36

How does prostate disease contribute to male infertility?

Answer 36

Prostate metabolizes more testosterone than it should

Question 37

Functions of testosterone

Answer 37

``` Masculinization Maturation/function of male repro tract Spermatogenesis Male sexual behavior Muscle mass/bone density (anabolic) Increased metabolism ```

Question 38

How does GnRH travel so that it is not metabolized by the liver and gets to the site of action in high concentrations?

Answer 38

Generated in the hypothalamus and then travels in the hypophyseal portal circulation to the pituitary gland.

Question 39

Describe the hypothalamo-hypophyseal-gonadal axis

Answer 39

GnRH is produced in the hypothalamus and sent to the pituitary via the hypophyseal portal vessels. The pituitary then releases FSH and LH, which travel to either the ovaries or testes and causes them to produce estrogen, progesterone, or androgens (and inhibin). Production of these hormones feeds back to the pituitary and hypothalamus to inhibit production of GnRH. If less testosterone is reaching the brain, the hypothalamus will be signaled to produce more GnRH.