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Pharmacology > Androgens pharmacology > Flashcards

Androgens pharmacology Flashcards

1
Q

the principal androgen secreted in men and women.

A

Testosterone

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2
Q

precursors with weak androgenic properties.

A

Androstenedione and DHEA (dehydroepiandrosterone)

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3
Q

Testosterone is synthesized from? in?

A

from cholesterol in the leydig cells, corpus luteum and adrenal glands.

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4
Q

Secretion of testosterone

A

Secretion of testosterone begins in the fetal testes in the first trimester.
Beginning of second trimester 250ng/dl, thereafter falls.
At birth 250ng/dl and falls again.
2-3 months after birth, rises to 250ng/dl.
Falls to 50ng/dl at 6 months.
Early adulthood, 500 to 700ng/dl in men.

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5
Q

Secretion of testosterone in women

A

Women: 30-50ng/dl

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6
Q

Maximal secretion of testosterone at ? lowest secretion of testosterone at ?

A

Secretion of testosterone is pulsatile and diurnal
Maximal secretion at 8am and lowest secretion at 8pm

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7
Q

Regulation of Testosterone

A

Principal stimulus for secretion is LH potentiated by FSH.
LH secretion is positively regulated by GnRH.
Testosterone directly inhibits LH secretion.

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8
Q

Pharmacokinetics of Testosterone ADME

A

8mg produced dly
Plasma level of testosterone is 0.6mcg/dl after puberty in men and 0.03mcg/dl in women.
About 40% is bound with high affinity by SHBG.
60% is bound with low affinity by albumin.
Metabolism is to dihydrotestosterone and estradiol which are active.
Degradation of testosterone occurs mainly in the liver to androsterone and ethiocholanolone are inactive metabolites.
Androsterone and ethiocholanolone conjugates are excreted in urine.
DHT is metabolised to androsterone, androstanedione and androstanediol.

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8
Q

Pharmacodynamics of Testosterone; MOA

A

Action is by interacting with androgen receptor (testosterone or DHT) or by interaction with estrogen receptor via aromatization to estradiol.
Androgen receptor (NR3A) is a transcription factor.
NR3A consist of amino-terminal, ligand binding and DNA binding domains.
Although testosterone itself is the active ligand in muscle and liver, in other tissues (e.g cells of the prostate, seminal vesicles, epididymis, and skin) it must be metabolized to derivatives, such as DHT.

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9
Q

testosterone is converted to DHT by?

A

by 5α-reductase

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10
Q

testosterone is converted to estradiol by?

A

CYP19 aromatase

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11
Q

actions of testosterone; Direct effects of testosterone and effects mediated indirectly via dihydrotestosterone or estradiol

A

Direct effects; Internal Genitalia, Wolffian development during gestation
Skeletal Muscle; increased mass and strength during puberty. Erythropoiesis, Bone growth.

Indirect via DHT; External Genitalia differentiation during gestation, maturation during puberty, adulthood prostatic diseases.
Hair Follicles: increased growth during puberty

Indirect via Estradiol; Bone-epiphyseal closure, increased density
Libido

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12
Q

Effects of androgens; In utero (3)

A

Stimulation of the differentiation of the Wolffian duct into male internal genitalia.
Development of the male external genitalia.

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13
Q

Effects of androgens; puberty

A

Puberty:
Development of seminiferous tubules.
Increased length and width of the penis.
Rugation of the scrotum.
Onset of secretion by the prostate gland.
Increased sebum production.
Onset of growth of axillary, pubic, body and facial hair.
Increased muscle mass and strenght.
Reduction in subcutaneous fat.
Increased erythropoiesis.
Acceleration of epiphyseal bone growth
Thickening of the larynx.
Development of libido.
Development of male aggression.

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14
Q

Effects of androgens; adulthood (3)

A

Adulthood:
Development of male pattern baldness.
Prostatic hyperplasia

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15
Q

Effects of androgen deficiency; During first trimester

A

incomplete sexual differentiation or dev. of female external genitalia, failure of differentiation of Wolffian ducts.

16
Q

Effects of androgen deficiency; 3rd trimester

A

, microphallus, cryptorchidism.

17
Q

Effects of androgen deficiency; Before completion of puberty

A

impairment of secondary sexual characteristics, eunuchoidism, gynecomastia.

18
Q

Effects of androgen deficiency; After completion of puberty

A

decrease of libido and energy, gradual regression of the pubertal effects of testosterone.

19
Q

enumerate Androgen preparations (4)

A

Testosterone esters
17α-Alkylated androgens
Transdermal delivery systems.
Others: 7α-methyl-19-nortestosterone (trestolone), Tetrahydrogestrinone.

20
Q

examples of Testosterone esters

A

hint; ECUT
testosterone enanthate, testosterone cypionate, testosterone undecanoate.

21
Q

examples of 17α-Alkylated androgens

A

stanozolol, danazol, methyltestosterone

22
Q

Indications/ Uses of androgens

A

Male hypogonadism.
Treatment of endometriosis.
Management of breast engorgement.
Management of anemia.
Perfomance enhancer in sports.
Growth stimulant in boys with delayed puberty
Catabolic and wasting states.
Angioedema.
Male contraception.

23
Q

Adverse effects of androgens

A

Masculinization.
Increased susceptibility to atherosclerosis.
Sodium retention and edema.
Hepatic dysfunction.
Prostatic hyperplasia.
Azoospermia .
Hepatic tumours.
Behavioural abnormalities.

24
Q

list the Anti-androgens drugs

A

Inhibitors of testosterone secretion.
Inhibitors of androgen action; Androgen receptor antagonists
5α-reductase inhibitors

25
Q

examples Inhibitors of testosterone secretion. (3)

A

GnRH analogues downregulate the GnRH receptors and inhibit testosterone secretion.

GnRH antagonists e.g abarelix for prostatic Ca.

Ketoconazole and similar antifungals block synthesis of steroid hormones.

26
Q

examples of Inhibitors of androgen action.
Androgen receptor antagonists

A

hint;lutamide
These are flutamide, bicalutamide, nilutamide, cyproterone, cyproterone acetate and spironolactone.

27
Q

Flutamide , dosage, adr, use

A

Substituted anilide.
Administered 3 times daily.
Used in conjunction with a GnRH analog in treating metastatic prostateCa.
very effective for treating hirsutism in women
Side effects include gynecomastia and hepatotoxicity.

28
Q

Bicalutamide, dosage, adr, use

A

Administered once daily.
Causes less hepatotoxicity.
Also used in managing metastatic prostate cancer.

29
Q

Spironolactone , adr, use

A

Competitive inhibitor of aldosterone and DHT.
Also reduces 17α-hydroxylase activity.
Used in treatment of hirsutism in women.

30
Q

Cyproterone and cyproterone acetate

A

They are used in treatment of hirsutism in women.
Also used for decreasing xcessive sexual drive in men.

31
Q

Finasteride, use, adr

A

Blocks the conversion of testosterone to DHT.
Onset of action is about 8 hours and lasts for about 24 hours.
Half-life is about 8 hours.
Developed for treatment of BPH.
Also approved for the treatment of male pattern baldness.
Also effective for treatment of hirsutism.
Impotence is an important side effect of its use.

32
Q

examples of 5α-reductase inhibitors

A

finasteride,
dutasteride

33
Q

treatment of hirsutism. (5)

A

Finasteride,
sipronolactone,
flutamide,
cyproterone and
cyproterone acetate

Pharmacology (11 decks)

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