Mne Lecture 32 - Sex Steroid Synthesis

Front 1

Androgens are composed of how many carbons?

Back 1

C19

Front 2

The conversion of cholesterol of pregnenolone is identical in the adrenal, ovary and testes. What controls the synthesis in each of these tissues?

Back 2

Adrenal:: ACTH
ovary and testes: LH

*synthesis of testosterone in the testes is similar to that in the adrenals

Front 3

What are the two ways the steroid can undergo 3b-hydroxylation and d4-d5 isomerization?

Back 3

1. the progesterone (d4) pathway
*used preferentially in humans

2. the dehydroepiandrosterone (d5) pathway

Front 4

Where are the enzymes for testosterone synthesis located?

Back 4

The SER

Front 5

What enzyme contains both 17-a-hydroxylase and C17-20 lyase activity?

Back 5

one cytochromone p450 enzyme

Front 6

What is the major steroid produced by the testes?

Back 6

-testosterone

Front 7

3 major testosterone derivatives are:

Back 7

1. dihydrotestosterone (DHT)
2. Androstanediol
3. Estradiol

Front 8

Testosterone ---> DHT

enzyme?

Back 8

enzyme = 5a-reductase
*requires NADPH

this occurs primarily in target tissues and is the active form of the hormone for many tissues

Front 9

Androstanediol

Back 9

-another potent androgen, in which the 3-ketone group of DHT has been reduced to form a hydroxyl group by 3a-reductase

Front 10

Estradiol

Back 10

-produced in some tissues (including the testis) by aromatization of the A ring.
-in some tissues, such as the brain of rats during sexual programming, this can be the active form of the hormone
-an aromatic a ring precludes the presence of a methyl group on position 10
ie. C19 is missing and estrogens have 18 carbons!

Front 11

Testosterone binds to?

Back 11

-TeBG (testosterone binding globulin) aka sex hormone binding protein (SHBG)
-albumin

% free?

Hint 11

1-3%

Front 12

Dihydrotestosterone binds to?

Back 12

TeBG (testosterone binding globulin)

% free?

Hint 12

1%

Front 13

Estradiol binds to?

Back 13

TeBG ( (testosterone binding globulin) --> binding is weak

Front 14

Estrone binds to?

Back 14

Albumin

Front 15

Progesterone binds to?

Back 15

CBG

Front 16

TeBG is produced where?
is it glycosylated?
what increases its synthesis?
what decreases its synthesis?

Back 16

-In the liver !
-It is a glycosylated protein
-Its synthesis is increased by estrogens, liver disease, and hyperthyroidism.
-Its synthesis is decreased by androgens, advanced age, and hypothyroidism

Front 17

What does LH do?

Back 17

-induces the Leydig cells of the testis to produce testosterone by activating adenylate cyclase
-this controls the first step in the conversion of cholesterol to testosterone --> side chain cleavage to form pregnenolone

Front 18

What does FSH do?

Back 18

-induces the leydig cells to produce more LH receptors

-acts on the sertoli cells of the testis to produce androgen-binding protein (ABP); testosterone also acts on these cells to synergize the effects of FSH

Front 19

What does testosterone inhibit?

Back 19

Testosterone inhibits the release of gonadotropin releasing hormone (GnRH) from the hypothalamus and may also have a negative feedback effect on the pituitary production of LH

Front 20

What is ABP ? How does it compare to TeBG?

Back 20

A glycoprotein that binds testosterone and helps to "bathe" the seminiferous tubules in high levels of hormone. It is the identical gene to TeBG, but it has a different glycosylation pattern.

The Main product of sertoli cells: androgen protein ABP. A carrier of androgens. Used to have a high level of androgens at all time in the testes
-ABP is the same as sex hormone binding globulin (different glycosylation pattern)

Front 21

What do the sertoli cells of the testis produce?

Back 21

1. androgen binding protein
2. inhibin, a peptide hormone that inhibits the release of FSH from the pituitary

Front 22

Examples of genes controlled by testosterone include:

Back 22

1. ABP
2. PSA
3. alpha2u globulin

Front 23

In general, androgens are involved in:

Back 23

-sexual differentiation
-spermatogenesis
-development of secondary sexual organs
-anabolic metabolism
-male pattern behavior

Front 24

Where are androgen receptors located?

Back 24

they have nuclear receptors !

hormone enters the cell by diffusion.

Front 25

Which has a higher affinity for androgen receptor: DHT or testosterone?

Back 25

In many target cells, testosterone is converted to dihydrotestosterone, which has a higher affinity for the androgen receptor than testosterone itself!!!

Front 26

Primary hypogonadism

Back 26

-Testicular failure leading to failure to develop secondary sex characteristics or regression of these characteristics
--> depends on the time of onset of the disease (can have onset during embryogenesis, early in life, late in life)
-->Infection, castration, most often it’s failure of enzyme in the testes in testosterone production pathway.

-often due to genetic deficiency of an enzyme required for testosterone production

**inability to make testosterone in the TESTES
(v. 2' hypogonadism where you cant make testosterone but it's a problem with the pituitary gland secretion of gonadotropins)

Front 27

Secondary hypogonadism

Back 27

-defective secretion of gonadotropins

**inability to produce testosterone due to issues w the pituitary
(v. 1' hypogonadism where you can't make testosterone in the testes, which is often due to a genetic deficiency of an enzyme required for testosterone production)

Front 28

5a-Reductase deficiency

Back 28

-inability to produce DHT, but do have testosterone!
-internal genitalia are male
-external genitalia are female
-inguinal testes are present that give rise to androgens at puberty leading to masculinization
__
5 alpha reductase deficient male at birth:
- is going to have testes since he's XY. but those testes likely to be inguinal testes.
-Penis will be present, but penis responds mainly to DHT not testosterone really (testosterone --> DHT) so they have more of a clitoral like penis than a true penis
-they have an opening for urethra meatus which is now at the female position, not the male position. ** NOT at the tip of the penis anymore
-down below there is an opening, looks like it might lead to vagina but it’s really just a blind pouch

SO if you’re born 5-a reductase deficient. They’re going to think you’re female because you have no penis, you have an opening which could lead to a vagina and the labia haven’t fused. The opening to urethra is not where the penis tip is.

-In some countries when this is not diagnosed as birth, brought up as female, but really you’re XY. If you’re male, what happens when testes respond to LH? Going to get growth of the penis. Get testes which come down and descend. Still have opening to vagina/vaginal pouch and urethral meatus stays in same place, but you begin to look more like a male.

Front 29

Testicular feminization syndrome

Back 29

-no functional androgen receptors
-XY (male) genotype
-patients have testes that produce testosterone but have complete feminization of external genitalia

Front 30

Benign prostatic hypertrophy

Back 30

-occurs in 75% of men over 60
-although it is poorly understood, androgens and estrogens appear to play a role in the uncontrolled growth of prostate cells.

Front 31

Aromatase

Back 31

-a complex process that involves 3 hydroxylations each of which requires O2 and NADPH
-the aromatase enzyme complex includes a P450 mixed function oxidase

Front 32

What do the following cells make:
-corpus luteum
-granulosa
-theca

Back 32

-corpus luteum:
a. progesterone
b. some 17b-estradiol (e2)

-granulosa:
a. 17b-estradiol

-theca
a. 17a-hydroxyprogesterone
b. androstenedione --> estrone E1 + 17b-estradiol (in the granulosa cells)
c. testosterone --> estrone E1+ 17b-estradiol (in the granulosa cells)

Front 33

80% of estradiol production in males is due to

Back 33

peripheral aromatization of testosterone

Front 34

50% of estradiol production in pregnant females comes from

Back 34

aromatization of adrenal androgens

Front 35

The major source of estrogens in postmenopausal women comes from

Back 35

the synthesis of estrone from adrenal androsterone

Front 36

Aromatase activity is found in which tissues:

Back 36

many which include, but are not limited to, the brain, skin, and fat

Front 37

How are E1, E2, and estriol disposed of?
Is this efficient in the body?

Back 37

-The liver converts E1, E2, and estriol to glucuronide or sulfate derivatives.
-This is not a particularly efficient process


*in general, conjugated steroids do not bind to the carrier proteins

Front 38

How is progesterone disposed of?
Is this efficient in the body?

Back 38

-The liver converts progesterone to the glucuronide derivative sodium pregnanediol-20-glucuronide.
-The rate of progesterone degradation in the liver is so efficient that oral progesterone is ineffective in humans.
-To overcome this, synthetic progestins are used which are not so readily conjugated by the liver
eg. 17a-hydroxyprogesterone derivatives

*in general, conjugated steroids do not bind to the carrier proteins

Front 39

Polycycstic ovary syndrome

Back 39

aka stein-leventhal syndrome

-overproduction of androgens causes hirutism, obesity, irregular menses, and impaired fertility

Front 40

Leydig cell and arrhenoblastoma tumors

Back 40

produce testosterone

Front 41

Granulosa-theca cell tumors

Back 41

produce estrogens

Front 42

intraovarian adrenal rests

Back 42

produce cortisol

Front 43

hydratiform mole

Back 43

produce lots of hCG

*also malignant transformation of hydratiform mole = choriocarcinoma

Front 44

osteoporosis

Back 44

-ovarian estrogen synthesis stops at menopause
-a weak estrogen, estrone, is made from adrenal androstenedione
-the levels may not be sufficient for bone mass upkeep

Front 45

What is baldness due to?

Back 45

-baldness is due to DHT
-high levels of testosterone --> dht --> baldness
-bald men don’t necessarily have lower sex drive, but do have lots of testosterone

-what about females who go bald?
Need high levels of androgen: testosterone --> DHT

Front 46

What drives sex drive?

Back 46

testosterone

Front 47

How is testosterone synthesis regulated?

Back 47

Unlike female where at menopause stop producing estradiol in males this process continues until you die

-control production of androgens from Leydig cells (make androgens)
-androgen feeds back on hypothalamus and pituitary
– normal feedback loopturns off GNRH, LH, FSH (pituitary LH and FSH have direct effect on testes)

-LH has direct effect on Leyudig cells, that stimulates androgen production

-testosterone is also going to affect the testes itself
--> testosterone is required for spermatogenesis at high levels.
-That can feed back on Sertoli cells in seminiferous tubules. 

-Sertoli cells can respond to FSH.

The Main product of sertoli cells: androgen protein ABP. A carrier of androgens. Used to have a high level of androgens at all time in the testes
-ABP is the same as sex hormone binding globulin (different glycosylation pattern) 

complicated feedback mechanism *series of hormones called inhibins and activins that can feed back on pituitary (but dont worry about this for now)

Front 48

What do men rub on their heads to inhibit hair loss?

Back 48

5-a reductase inhibitor --> rub on head to inhibit hair loss

Front 49

What happens when testosterone enters a cell?

Back 49

-When androgen comes into the cell, normally comes in as testosterone.
-Once its in the cell its converted to DHT or stay as testosterone.
-It then binds to receptor, (testosterone is on the top in image) brings about a series of effects

*DHT and Testosterone bring about a different series of effects, although some may overlap*

what does testosterone affect in embryogenesis:
-spermatogenes
-gonadotrpoin regulation
-sexual differentiation 
-to an extent wolffian stimulation

DHT is made by 5a-reductase. This is mainly active in:
-sexual maturation at puberty
-baldness
-external virilization (not looking like a woman)
-DOES NOT have feedback on effects on spermatogenesis.

Front 50

Why don't muscle builders get big penises?

Back 50

Androgens stimulate the penis, make it bigger

There are no receptors in adult penis for androgens. Can give as much as you want won’t get growth. 

That’s why muscle builders don’t get huge penises.

what is going on? Why do you need androgens when your young but not older?
--> Young have receptors, 9 yo can give androgens or give androgens and penis grows. 
-->When it comes to some set length it loses its receptors stops growing

Front 51

How do you find out the find out the real erect length of a penis?

Back 51

1. Inject penis
2. Can stretch it
-->need a pound of force (450g)
-->when you give that much force you can determine what the erect length is going to be

Front 52

What is micropenis defined as? What is the normal range? Largest on record?

Back 52

Micropenis
--> 2 in or less when erect;
--> other papers 4 inches or less

Maximum length
--> (recorded) 13.5 inches erect

average
--> just over 5 inches
-->mean is higher than the median
-->median more like 5 or slightly less than 5 (because some people are much more endowed than others)

Front 53

Male v. Female 1' sexual development during gestation:
What chromosomes, what hormones affect what?

Back 53

-On left have a male
-males are XY in humans
-that means we’re going to develop the testes --> genetic predisposition, nothing to do with androgens (make testes whether you can make androgens or not)
-MALES: mullerian inhibiting factor, no mullerian duct, no uterus
-going to produce testosterone early in life as soon as testes are made
-testosterone made early in life allows formation of wollfian duct, vas defferens, epidimidys, seminal vesicles
-DHT --> main effect are on penis, penile urethra, and scrotum

what about females? 
-XX
-no Y chromosome, no testes
-develop ovary, make estradiol
-ovary does NOT make mullerian inhibiting factor, get mullerian duct, do get uterus, fallopian tube, and upper vagina
-estradiol itself affects clitoris, vagina, labia, lower vagina

Front 54

How does the external development of the genitalia differ between males and females during gestation? What are the big morphological changes?

Back 54

-Start off things the same
-during embryogenesis turn into male/female
-what is the clitorous in female getting bigger into penis in male
-labia fuse in male
-urethra opening moves upward to the tip of the penis (from female position to the male position)
-end up with male and female.

Front 55

Why do males and females start developing pubic hair?

Back 55

Due to androgens, which are required for all sex hair (hair that happens during puberty)
eg. coarse hair on arms, under arms, legs, pubic hair, chest,

during puberty, first pubic hair due to androgens from adrenal cortex. It’s called adrenarche. Adrenarche is the sudden production of relatively large amounts of androgens which some people think starts pubtery. It’s not the testes. 

__
From wiki:

Adrenarche is an early sexual maturation stage in some higher primates that in humans typically occurs at around 6 to 8 years of age. During adrenarche the adrenal cortex secretes increased levels of androgens such as DHEA and DHEAS, but without increased cortisol levels. Adrenarche is the result of the development of a new zone of the adrenal cortex, the zona reticularis.[1] Adrenarche is a process related to puberty, but distinct from hypothalamic-pituitary-gonadal maturation and function

Front 56

Complete androgen insensitivity (CAIS)

Back 56

This is a male who cannot produce androgen receptors/androgen receptors don’t work

-everything that occurred w 5-a reductase is going to occur.
-Going to get testes because you’re a genetic male, but cannot respond at all to androgens therefore you look female.

this is a male past puberty note:
-no pubic hair (totally dependent on androgen receptor, which is true in males and females)

-no axillary hair (underarm hair)

-what about breast development? Why would male develop breasts?
-->No ovaries, only testes
-->AROMATASE converts androgen to estradiol and gives you estradiol.
-->No receptors, need receptors for all the feedback of androgen production
-->If you’re producing androgens, in a normal person feed back to pituitary and hypothalamus and turn off production
-->this person doesn’t have androgen receptors and cannot turn off androgen production. Get high estradiol production, much more than a normal male.


___

CAN ALSO HAVE PAIS:
Partial Androgen receptor deficiency
-get high estradiol production
-do produce some testosterone, but aromatase converts it to estradiol and get this effect.

Front 57

Gynecomastia

Back 57

-inappropriate growth of breast in males
-caused by estrogen stimulation
-both glandular and adipose tissue is present

Front 58

The prevalence of gynecomastia in the normal adult population is high or low?

Back 58

HIGH

- 25% of army recruits during world war 2 had measurable breast devo

-Up to 70% of older adult males (30-50% in younger males)
-->since testosterone decreases and estradiol increases

-Higher incidence in obese males
-->Aromatase also present in fat tissue, the more fat tissue you have the more aromatase the more estradiol you make.Think of someone who is really obese, think of their chest, think of breast development because of obesity. 

-Very high in atheletes abusing anabolic steroids
-->see in muscle builders:
-often take Anabolic steroids (which are androgens)
-if they are aromatized they make estradiol 
-that’s why if you’re a muscle builder taking anaboic steroids you also prob take an estrogen antagonist to prevent the side effects of estrogen

-Males undergoing puberty often have transient gynecomastia (~50%)
-->Take a male during puberty they’re producing low levels of androgen just before puberty and then they make a lot of androgens
-->in adult male, not that much aromatase activity so androgens affect muscle growth, if they havent reached final height yet it affect height, aggression
-->during puberty, aromatase levels really high, stay high into puberty. That aromatase converts testosterone to estradiol get breast development
-->large percentage of males going through puberty get breast development, it all really depends on when aromatase is turned off. If it’s turned off early you won’t get it, if it’s turned off later you will get it. Goes away, usually.

Front 59

How can you prevent/treat gynecomastia?

Back 59

-Hard to prevent breast development in males.
-If you’re taking a drugs just stop taking them
-aromatase inhibitors don’t really work
-surgery is an option.

Front 60

How do we make estradiol, estrone, and progesterone? Where is each made???

Back 60

make progesterone and estradiol from same tissue --> the OVARIES. 

BUT we have a problem: progesterone is precursor for estradiol, so we have to separate pathways out otherwise we won’t be able to control progesterone and estradiol conversion separately

HOW do we do this?
-We use theca cells and granulosa cells
-in the THECA cells go from cholesterol down to progesterone down to androstenedione down to testosterone. No aromatase. Go through the normal pathway and you can’t go any further.
-In the GRANULOSA cells, can go from cholesterol --> pregneolone --> progesterone but cant do anything else, no 17a hydroxylase. This is progesterone is now secreted.
**WE GET PROGESTERONE FROM GRANULOSA CELLS.**

How do we make estradiol?
-Take androgens from THECA cells (androstenedione and testosterone) and convert to estradiol and estrone
-Adult female, mostly estradiol production.

**1 cell type --> regulate and produce two different types of hormones.

Front 61

Where do you produce hormones when you're pregnant?

Back 61

Pregnant female:
-produce everything in placenta because they no longer have an active ovary producing estradiol
-now produce everything from placenta: progesterone and estriol (E3).

-placenta doesn’t take cholesterol and go through the whole pathway, rather it uses precursors that come from the ADRENAL.
-The adrenal takes pregnenolone, converts it to DHEA and DHEA sulfate (more soluble form) which goes to liver. -The liver has a 16-a-hydroxylase, which puts -OH on the 16 position.
-This goes to placenta, aromatase adds another -OH group then you get estriol. (ignore degradation pw)

We also need to make glucocorticoids in the adrenal. How do we do that?
-Don’t actually go down to progesterone, don’t make that in the fetus, so we need to get it from somewhere else.
-We get it from the placenta.
-Prenenolone in the placenta goes to progesterone which then gets converted to cortisol in the fetus. all this is due to the enzymes that are present / not present in these tissues.Note enzymes at bottom of slide.

Front 62

What does ER look like when bound to DES (a synthetic estrogen) ?
What does ER bound to tamoxifen look like?

Back 62

What does ER look like when bound to DES (a synthetic estrogen) ?
-here is the crystal structure of ER bound to DES
-notice helix 12 --> helix 12 interacts with coactivators that affect transcription

What does ER bound to tamoxifen look like?
-tamoxifen bound --> note that helix 12 in different position. 
-Interacts with transcription factors, but it’s different. Perhaps a different set, either quantitatively or qualitatively it’s different.
-This means that tamoxifen has the BONE SAVING effects of estradiol
--> in females, the main reasons you have good bones is because of estradiol. That’s why you get osteoporosis after menopause. In males, it’s testosterone (but not testosterone itself, more likely estradiol converted from testosterone). That’s why males don’t have osteoperosis as much in old age because they’re still producing testosterone.
-This form of estrogten receptor does have a differential effect in breast cancer. In breast cancer estrogens stimulate growth. Tamoxifen prevents that stimulation, it doesn’t stimulate growth, and because you have a very high level of tamoxifen pharmacologically, it prevents estradiol binding. When you get this form of receptor will allow good actions of estradiol (bone protection) but not bad (breast cancer growth). Also note raloxifene does this too!

Front 63

Raloxifene

Back 63

an oral selective estrogen receptor modulator (SERM) that has estrogenic actions on bone and anti-estrogenic actions on the uterus and breast. It is used in the prevention of osteoporosis in postmenopausal women.

Front 64

SERM

Back 64

Selective ER modulator (SERM)

eg. tamoxifen, raloxifen

Front 65

DES

Back 65

-(a synthetic estrogen)
-marketed to prevent miscarriage, abortion, and premature labor from 1938 to 1971
-A prospective, blinded, placebo controlled study reported in 1953 found that DES was ineffective in preventing miscarriage
-In 1971, the FDA issued a drug bulletin contraindicating the use of DES in pregnancy
-Nations continued to ban or restrict its use into the 1980s
-there was no increase in and of the positive parameters, but it did have devastating effects on offspring

-Patients prescribed DES during pregnancy are at a modestly increased risk for breast cancer

-DES daughters are at increased risk for
a.Clear cell adenocarcinoma (CCA) of the vagina and cervix
b. Reproductive tract structural differences
c. Pregnancy complications
d. Infertility(taking in synthetic estrogen during pregnancy, this synthetic estrogen affects the fetus.)

-DES sons are at an increased risk for epididymal cysts (no major risks, probably have a way to overcome this anyway if you think about it)

-DES grand kids have no confirmed health risks.