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Y3 Patient sem 1 > Male hormones and reproduction > Flashcards

Male hormones and reproduction Flashcards

1
Q

What is the bio-synthetic precursor for all steroid hormones?

A

Cholesterol

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2
Q

Describe the pathway for progesterone

A

Acetate -> cholesterol -> pregnenolone -> progesterone

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3
Q

What are 3 androgens?

A
  • Androstenedione
  • Testosterone
  • Dihydrotestosterone (DHT)
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4
Q

Describe the pathway for DHT

A

Acetate -> cholesterol -> pregnenolone -> progesterone -> Androstenedione -> Testosterone -> DHT

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5
Q

What are 2 oestrogens?

A
  • estrone

- 17beta-estradiol

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6
Q

What is estrone converted from?

A

Androstenedione –> estrone (by aromatase)

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7
Q

What is 17beta-estradiol converted from?

A

Testosterone –> 17beta-estradiol (by aromatase)

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8
Q

What 2 hormones are needed for male reproductive function?

A

Estrogens and Progesterone

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9
Q

When is the progesterone level the same in males and females?

A

During the non-luteal phase

progesterone levels rise in the luteal phase

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10
Q

What is spermiogenesis?

A

Production of mature, motile spermatozoa

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11
Q

Name 5 parts of the male reproductive tract

A
  1. Testis
  2. Epidiymis
  3. Ductus deferens
  4. Accessory glands
  5. Urethra
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12
Q

What is the function of the Testis?

A

Sperm production, steroid hormone production

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13
Q

What is the function of the epididymis?

A

Sperm collection and maturation

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14
Q

What is the function of the ductus deferens?

A

Transport and storage

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15
Q

What is the function of the accessory glands?

A

Contributions to seminal fluid

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16
Q

What is the function of the urethra?

A

transport

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17
Q

Specifically, where is sperm produced?

A

In the seminiferous tubules of the testis

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18
Q

As sperm cells mature where do they move?

A

They move inwards towards the lumen

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19
Q

What cells are important during the movement of sperm to the epididymis ?

A

Myoid cells

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20
Q

Where does the biosynthesis of testosterone occur?

A

Mostly in Leydig cells

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21
Q

How is testosterone converted into DHT?

A

catalysed by 5alpha-reductase and NADPH

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22
Q

Where is testosterone converted into DHT?

A

Conversion takes place in the Sertoli cell

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23
Q

What is the most active androgen?

A

DHT

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24
Q

What family of receptors do receptors for all major classes of steroid hormone belong to?

A

Nuclear receptor superfamily

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25
Q

What are the features of the receptors in the nuclear receptor superfamily?

A
  • They are proteins with 2 binding sites; one for steroid and the other for DNA
26
Q

What happens when a steroidal ligand binds to receptor?

A
  • produces a complex that acts on DNA
  • the complex then acts on DNA and alters the repertoire of genes being expressed by target cells
  • THIS activity defines the steroid receptors as transcription factors
27
Q

What do androgens interact with?

A

Androgen receptors (AR)

28
Q

What cell populations express AR?

A
  • All major cell populations in the testis, epididymis and accessory glands
  • Also found in tissues where secondary sexual characteristics appear
29
Q

Why is androgen-AR binding necessary?

A

The various cell types require androgen-AR binding to fulfil their respective roles in sperm production, transport and activation

30
Q

What are androgens responsible for?

A

The development of secondary sex characteristics (genital enlargement, sperm growth and maturation etc), anabolic effects and spermatogenesis

31
Q

What controls sex steroid production?

A

Gonadotrophins (LH and FSH) - both expressed in male at constant levels

32
Q

Where are the gonadotrophins secreted from?

A

Anterior pituitary

33
Q

What causes the secretion of gonadotrophins?

A

The secretion of gonadotrophin releasing hormone (GnRH) from the Hypothalamus
- pulsatile release, constant frequency

34
Q

What do the sex steroids control?

A

Sperm production (ejaculate) and maturation

35
Q

What is produced in the testis?

A
  • spermatozoa

- sex steroids

36
Q

How do gonadotrophins enter cells?

A

By binding to receptors on the cell surface (polypeptide hormones can’t pass cell membrane - hydrophillic)

37
Q

Where does FSH bind ?

A

To the FSH receptor on the surface of a sertoli cell

38
Q

Where does LH bind?

A

To the LH receptor on the surface of the Leydig cell

39
Q

Where is Testosterone transported once it is produced in the leydig cell?

A

To the sertoli cell

40
Q

What is produced in the sertoli cell?

A

Androgen-binding protein (ABP)

41
Q

What does ABP bind to?

A

Binds to testosterone and DHT and concentrates them in the luminal fluid of the seminiferous tubules and downstream regions of the male tract and is released as a complex by the sertoli cell

42
Q

What does the release of a ABP-steroid complex from the sertoli cell stimulate?

A
  • spermatogenesis in the seminiferous tubules,
  • sperm maturation in the epididymis
  • accessory gland secretions
  • myoid cell contractile activity to propel sperm along the tract
43
Q

What else happens in the sertoli cell?

A

5-alpha reductase converts T to DHT

44
Q

Where do complex’s travel to once they have left the sertoli cell?

A

To the epididymis

45
Q

What feedback is included for testosterone?

A

purely negative feedback: testosterone and inhibin inhibit the secretion of GnRH by the hypothalamus and LH and FSH by the pituitary

46
Q

What are sperm maturation stages dependent on?

A

Androgen-dependent (Sertoli cell nurse function)

47
Q

What is required to move released sperm along the seminiferous tubule?

A

Myoid cell contractility. They are AR-positive, action is androgen-dependent

48
Q

How do sperm exit the sertoli cell?

A

Tail first and move towards lumen (not yet motile!!)

49
Q

Where is the ability to swim initially acquired for sperm?

A

In the epididymis (DHT-dependent) with futher FULL activation in the female tract

50
Q

When does spermeogenesis occur?

A

Post meiosis

51
Q

What is the normal volume of ejaculate?

A

1.5-5.0 ml

52
Q

What is included in the composition of the ejaculate?

A
  • Epididymis & Ductus deferens (sperm-rich fraction): 5% of the ejaculate volume
  • Prostatic secretion: 13-33% of the ejaculate volume
  • Seminal vesicle secretion: 46 – 80% of the ejaculate volume
  • Bulbo-urethral gland secretion: 5% of the ejaculate
53
Q

What is erection?

A

erectile tissue [corpus cavernosum and corpus spongiosum] becomes engorged with blood, arterioles dilated as a result of parasympathetic nervous system activity

54
Q

What are emission and ejaculation controlled by?

A

Sympathetic nervous system

55
Q

What is erectile dysfunction?

A
  • Pathological bases – psychogenic; neurogenic; vascular and endocrine
  • Latrogenic causes of impotence – many drugs including tricyclics and SSRIs ; antihypertensives including beta blockers and calcium antagonists
56
Q

How is erectile dysfunction managed?

A
  • PGE1 – alprostadil

- PDE5 inhibitors – eg sildenafil (inhibits the breakdown of cAMP)

57
Q

What are the risk factors for prostate cancer?

A
  • age
  • ethnicity
  • family history
58
Q

What are the symptoms of prostate cancer?

A
  • Urgent and frequent urination
  • Nocturnal enuresis (involuntary urination)
  • Difficulty starting or emptying the bladder
  • Urine flow weak, interrupted or difficult to control
  • Back or pelvic pain
59
Q

What is included in the pharmacological management of prostate cancer?

A
  • Gonadorelin (GnRH) agonists and antagonists
  • Androgen antagonist – cyproterone acetate (effective provided keeps androgen dependency of normal prostate)
  • 5-a-reductase inhibitors – dutasteride & finasteride (blocking DHT – more active)
60
Q

What does exogenous Testosterone lead to?

A

Decreased LH and FSH and decreased fertility (used as contraception in males?? - would need very high doses as its difficult to completely inhibit sperm production)

These may lead to iatrogenic hypogonadotrophic hypogonadism
Testosterone undecanoate – longer acting depot, better PK (eg Nebido ™)

Y3 Patient sem 1 (22 decks)

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