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Physiology & Science: Reproduction > Pharmacology of androgens and anti-androgens > Flashcards

Pharmacology of androgens and anti-androgens Flashcards

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1
Q

Where are androgens secreted from?

A
  • testes, ovary + adrenal cortex secrete androgens - steroid sex hormones
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2
Q

The testes (leydig cells of testes) secrete testosterone. What is it synthesised from in Leydig cells?

A

cholesterol

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3
Q

Secretions from the adrenal cortex are under the influence from which hormone? Also where in the adrenal cortex are androgens made?

A
  • ACTH
  • androgens made in zona reticularis
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4
Q

What does inhibin B do?

A
  • produced by granulosa cells in ovary / sertoli cells in testes
  • downregulates FSH synthesis
  • inhibits FSH secretion
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5
Q

What is FSH important for in males?

A
  • sertoli cells
    • spermatogenesis
    • AMH -> regression of mullerian ducts
    • -> inhibin B -> -ve feedback
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6
Q

Describe the pathway of synthesis for testosterone

A

cholesterol -> pregnenolone -> progesterone -> androstenedione -> testosterone -> oestrogen

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7
Q

Testosterone is converted to DHT in most target cells (by 5-a-reductase), except where?

A

except in muscle

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8
Q

What is the difference in binding between testosterone and DHT to the receptor?

A
  • DHT + testosterone bind to same receptor
  • testosterone-receptor complex less stable
  • DHT more potent
  • DHT formation allows amplification of actions of testosterone
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9
Q

What are downstream effects of testosterone binding to its receptor?

A
  • gonadotrophin (LH + FSH) regulation
  • initiates + maintains spermatogenesis
  • sexual differentiation
  • wolffian duct stimulation (internal genitalia)
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10
Q

What additional downstream effects does DHT cause by binding to the testosterone receptor?

A
  • external virilsation
  • sexual maturation at puberty
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11
Q

Treatment of what disease makes use of the testosterone mechanism of action pathway?

A

prostate cancer

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12
Q

Why is male pattern baldness treated with 5a-reductase inhibitors?

A

DHT promotes hair loss

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13
Q

Where is type I 5a-reductase found?

A

scalp + skin

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14
Q

Where is type II 5a-reductase found?

A

genital skin + prostate

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15
Q

What happens when there is a deficiency in 5a-reductase?

A
  • testes develop
  • without prostate
  • external genitalia resemble those of females
  • raised as girls until puberty
  • some may adopt male role post-puberty (XY baby w female ext genitalia)
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16
Q

What is “penis-at-12-syndrome”?

A
  • clitoris enlarges
  • at puberty inc testosterone causes development of external male genitalia + secondary sexual characteristics
  • if the receptors are present
  • inc LH and testosterone levels at puberty
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17
Q

What would mutation in type II 5a-reductase lead to?

A
  • male pseudohermaphroditisim
  • comon in parts of Dominican Republic
  • born w primary sex characteristics of one sex but develops secondary sex characteristics that are different from what woud be expected on the basis of the gonadal tissue (ovary or testis)
18
Q

What may inadequate metabolism of DHT cause?

A
  • prostatic hyperplasia
  • acne, hirsuitism
19
Q

What regulatory effects does testosterone exert?

A
  • reduces secretion of GnRH
  • inhibits secretion of LH
20
Q

Testosterone acts via sertoli cells to initiate and maintain spermatogenesis. What are the idfferent structures it induces via the Wolffian Duct?

A
  • epididymis
  • vas deferens
  • seminal vesicles
  • ejaculatory duct
21
Q

Testosterone induces male secondary sex characteristics. What does it do to oestrogen?

A

opposes action of oestrogen on breast growth

22
Q

What behavioural and physical changes does testosterone induce?

A
  • provokes boisterous play
  • may enhance sex drive
  • aggressive behaviour
  • virilisation - deep voice, body hair, muscle gmulk
23
Q

What actions does testosterone have on bone growth?

A
  • anabolic
  • induces bone growth
  • cessation of bone growth
24
Q

What are the effects of testosterone and DHT on secondary characteristics in males compared to females?

A
  • height: on avg males are taller than females
  • muscularity: males are of greater muscularity, esp shoulder girdle than females
  • bone growth: males have stronger bone growth, greater shoulder to pelvic girdle ratio (GH secretion) than females - heavier skulls, larger hands + feet
  • deep voice: inc growth of larynx
  • pubic hair - continuous with abdominal + chest hair
  • prominent subcutaenous veins due to lack of subcutaneous fat
25
Q

In many cases, several androgens (eg testosterone, nandrolone, oxymetholone etc) are used for prolonged periods and their continuous use can cause unwanted effects. What are some unwanted effects of testosterone?

A
  • hypertension + oedema: testosterone + other anabolic steroids such as nandrolone, stanozolol have calcium, sodium + water-retaining actions
  • cholestatic jaundice: anabolic steroids (nandrolone, stanozolol) may lead to liver cancer
  • suppression of gonadotrophin release w/ testicular regression + reduced spermatogenesis
  • virilisation; hirsuitism; male pattern baldness; acne
  • premature closure of epiphyses of long bone in boys
  • gynaecomastia - due to conversion of testosterone to oestrogens by aromatase
26
Q

Why do body builders and athletes take steroids/testosterone?

A
  • large doses may be effective in increasing muscle mass / athletic performance in some individuals
  • all anabolic steroids virilise
  • attempts to separate the anabolic from virilising effects of anabolic steroids have been unsuccessful
27
Q

What are the effects of (abuse of) anabolic steroids?

A
  • lower testicular size + sperm count
  • changes in libido, regression of testes w/ suppression of spermatogenesis
  • increased aggression
  • hepatotoxicity w/ cholestasis, hepatitis or hepatocellular tumours
  • increased LDL and decrease HDL -> vascular disease
  • weight gain
  • acne

stanozolol, nandrolone + other anabolic steroids can be detected in the urine of atheletes abusing these drugs

28
Q

Give an example of synthetic GnRH - how must this be administered?

A
  • gonadorelin
  • can be given but administration must be by pump
  • and given intermittently to avoid densensitisation + down-regulation
29
Q

Give examples of GnRH agonist analogues and their effects

A
  • buserelin, goserelin
  • desensitise after an initial surge of LH and FSH release + act as antagonists
  • cause reduction in testosterone in long term
  • useful for prostate + breast cancers, and endometriosis
30
Q

Give examples of GnRH antagonists and what they’re used for

A
  • cetrorelix
  • ganirelix
  • cause no initial surge in LH and FSH
  • so better used in IVF
31
Q

What is cryptorchidism?

A
  • retained testes
  • 97% of testes descend around birth + 99% by 1 yr
  • failure of testes to descend can potentially lead to testicular tumour formation + infertility
  • drug treatment or surgical remedy
32
Q

In which certain individuals are androgen antagonists used in?

A
  • Sex offenders
  • reduce libido to treat hypersexuality
  • must get informed consent
  • eg. cyprotorone acetate
33
Q

What is mesterolone used for?

A

male infertility associated w hypogonadism

34
Q

What is Danazol?

A
  • androgen derivative, but not converted to oestrogen
  • feedback inhibition on HPG -> decrease release of LH/FSH in both sexes
  • inhibits testicular + ovary function directly -> stops ovulation
  • has antioestrogenic and antiprogestogenic effects
  • used for gynaecomastia, mastalgia, benign fibrocystic disease, endometriosis + infertility, menorrhagia
35
Q

(primary problem) In chromosomal abnormalities such as Klinefelter’s (XXY) syndrome there is deficient -ve feedback at hypothalamic-pituitary levels w/ consequent high levels of LH and FSH. What is the treatment for this?

A
  • treat with testosterone (+ GH); puberty may take 2 years to reach completion
  • note that continuous administration of testosterone -> premature closure of epiphyses of long bones - so it’s better to dose for 4-6 months, stop + assess growth to avoid reducing final height
36
Q

What happens in Kallman’s syndrome and what is the treatment?

A
  • deficiency/absence of hypothalamic secretion of GnRH + hence low levels or absence of pituitary FSH and LH
  • treatment: give gonadorelin or LH + FSH - it may take months for their effects on spermatogenesis to develop in post-pubertal patients
37
Q

What is cyproterone acetate and its uses?

A
  • androgen antagonist
  • treat abnormalities of development of secondary sexual characteristics
  • inhibits peripheral androgen receptors
  • uses:
    • precocious puberty in boys
    • to suppress initial surge effects of goserelin and buserelin
    • acne, hirsuitism, virilisation in women
38
Q

What is benign prostatic hypertrophy and its treatment?

A
  • enlargement of prostate in older men causes urinary obstruction
  • drug treatment: 5a reductase blocker - stops DHT prod -> shrinkage of prostate
  • Finasteride has better utility as it inhibits type II 5a-reductase
  • Dutasteride has unclear utility as it inhibits types I + II 5a-reductase
39
Q

Testosterone and DHT stimulate the growth of prostatic cells. What is the drug treatment of prostate cancer?

A
  • cyproterone acetate
  • GnRH analogues (goserelin + buserelin)
  • GnRH antagonists (cetrorelix + ganirelix)
  • oestrogens (ethinyloestradiol + diethylstilbestrol)
  • anti-androgens (flutamide)
  • 5a-reductase inhibitors
40
Q

For erectile dysfunction, treatment with exogenous androgens may produce clinical improvement in signs of hypogonadism but may not improve sexual function. What drug would be useful for treating erectile dysfunction?

A
  • PDE5 inhibitors (eg. sildenafil) promotes following pathway:
  • release of NO during sexual stimulation
  • NO activates guanylate cyclase (GC) which releases cGMP from GTP
  • cGMP -> relaxation of sm mucles lining blood vessels
  • -> inflow of blood occurs
  • tumescence (erection)
  • generally without effect until stimulation begins
41
Q

Side effects of sildenafil?

A
  • headache
  • vasodilation
  • flushing
  • decrease BP
  • disturbances of colour vision due to inhibition of PDE6 in retina
  • do NOT take with nitrate drugs
  • incidence of priapism is low

Physiology & Science: Reproduction (18 decks)

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