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Case 11: Male Reproductive System > Hypogonadism > Flashcards

Hypogonadism Flashcards

1
Q

What does it mean when hormones are pulsatile & examples

A

Released at different frequencies & amplitudes
GnRH, LH & testosterone

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2
Q

What is the circadian rhythm of male endocrine system

A

Increases in early a.m 4:00-8:00
Decrease in late p.m 16:00-20:00

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3
Q

What is the feedback mechanism of endocrine system

A

Negative feedback

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4
Q

What is the 2 types of testing in endocrine system

A
  1. Standard testing
  2. Dynamic testing
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5
Q

What is the hypothalamo-pituitary-gonodal axis

A

Hypothalamus release GnRH that stimulate anterior pituitary to release FSH & LH
FSH act on Sertoli cells in testicles allowing for spermatozoa @ seminiferous tubules & release inhibin to inhibit release of FSH from anterior pituitary
LH act on Leydig cells in testicles that produce testosterone from cholesterol that also stimulate Sertoli cells to produce spermatozoa or go to target tissue
Testosterone also provides negative feedback to anterior pituitary & hypothalamus

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6
Q

What is androgens

A

Sex hormones with cholesterol as precursor

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7
Q

What is the 2 male androgens

A

Testosterone
Dihydrotestosterone

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8
Q

What is the 3 functions of androgens

A
  1. Masculination of genital tract
  2. Development & maintenance of male secondary sexual characteristics
  3. Anabolic effect on muscle mass, bone density & decrease fat mass)
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9
Q

What is the pathway of testosterone biosynthesis

A
  1. Cholesterol
  2. Pregnenolone to progesterone & DHEA
  3. Progesterone to mineralocorticoids & glucocorticoid
  4. DHEA & progesterone to androstenedione
  5. Androstenedione to oestrone & testosterone
  6. Testosterone to oestrodiol via aroma taste at liver/fat cells & DHT via 5-alpha reductase
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10
Q

What 8 factors affect testosterone production

A
  1. Sex difference
  2. Age
  3. Pulsatility
  4. Diurnal rhythm
  5. SHBG concentration
  6. Health state (stress, illness, diabetes, metabolic syndrome, obesity)
  7. Hyperprolactinaemia
  8. Medication
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11
Q

What is the 2 forms of testosterone

A
  1. Free that is active & bioavailable
  2. Bound to proteins
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12
Q

To what proteins do testosterone bind

A
  1. Sex hormone binding globulin that has high affinity & low capacity
  2. Albumin that has low affinity & high capacity & bioavailable
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13
Q

What is SHBG

A

Glycoprotein produced at the liver

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14
Q

What 3 things does SHBG bind

A

Testosterone, DHT, estrogen

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15
Q

What is the function of SHBG

A

Regulate bioavailability of sex hormones to tissue

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16
Q

What is used to provide an estimate of free testosterone

A

Free androgen index

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17
Q

3 examples of increased SHBG

A

Hyperthyroidism
Aging
GH deficiency

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18
Q

3 examples of decreased SHBG

A

Obesity
Hypothyroidism
GH excess

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19
Q

What is testosterone mechanism of action

A

Testosterone is synthesized & enter the cells (lipophilic molecule) & can be converted to DHT or directly bind to androgen receptor
If converted to DHT it then binds to androgen receptor in cytoplasm
After binding it gets translocated to nucleus, gene regulation, protein synthesis & target tissue effects

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20
Q

What is androgen insensitivity syndrome

A

Mutation of androgen receptor & dysfunctional receptors
Can be complete or partial

21
Q

What is the 3 places where DHT conversion occur

A

Prostate, skin & hair follicles

22
Q

What is the 3 functions of DHT

A
  1. Development of male external genitalia
  2. Prostate growth & function
  3. Secondary sexual characteristics
23
Q

What is the important enzyme that converts testosterone to DHT

A

5-alpha reductase

24
Q

What does hypogonadism mean

A

Decreased function of testes

25
What 2 things does hypogonadism affect
Sperm production Testosterone production
26
What 2 things does hypogonadism leads to
Infertility Loss of secondary sexual characteristics
27
Where does primary & secondary hypogonadism occur
Primary: testicular failure Secondary: hypothalamus or pituitary failure
28
What is chemical results of primary hypogonadism
High FSH & LH w/ low testosterone
29
What is chemical results of secondary hypogonadism
Low or inappropriate LH & FSH w/ low testosterone
30
What is another name for primary hypogonadism
Hypergonadotrophic hypogonadism
31
What is another name for secondary hypogonadism
Hypogonadotrophic hypogonadism
32
What is the causes of primary hypogonadism
Congenital: Klinefelter syndrome Acquired: damage to testes, infection, chemotherapy/radiation
33
What is causes of secondary hypogonadism
Congenital: Kallmann syndrome Acquired: tumors, systemic disease, medication, obesity & metabolic syndrome
34
What dynamic test is done w/ primary hypogonadism
HCG stimulation test
35
What 2 dynamic test is done w/ secondary hypogonadism
1. Clomiphene stimulation test 2. GnRH stimulation test
36
What is 3 clinical features of hypogonadism pre-natal
Affects primary male sex structures Incomplete virilization Cryptorchidism
37
What is 3 clinical features of hypogonadism before puberty
Lack of secondary sex characteristics Eunuchoid body proportion Delayed puberty
38
What is 6 clinical features of hypogonadism post puberty
Osteoporosis Fatigue & mood change Increased fat Gynaecomastia Decrease muscle Decrease libido & erectile dysfunction Testes atrophy & infertility
39
What is 4 clinical features of hypogonadism elderly
Same as adult Cognitive changes Andropause Insulin resistance, central obesity, increased CVS risk
40
Define gynaecomastia
Enlargement of male breast tissue
41
What is 4 causes of gynaecomastia
Idiopathic Obesity Hormonal imbalance Liver disease
42
How to test for gynaecomastia
Assess hormone levels Rule out underlying pathologies
43
How is total testosterone measured
8-10am To confirm hypogonadism test should be repeated on separate occasion
44
When to test LH & FSH
When confirmed low testosterone
45
When is LH & FSH high & low
High: primary Low/inappropriately normal: secondary
46
How does HCG test work
Tests Leydig cells function & mimic LH response to stimulate testosterone & normally increases
47
How does GnRH test work
Test HPG axis function by stimulating GnRH to stimulate LH/FSH release If hypothalamic disease LH & FSH should increase but if pituitary disease LH & FSH will not increase
48
How does clomiphene test work
Tests hypothalamic-pituitary response by inhibiting estrogen feedback & GnRH should increase in secondary but not in primary

Case 11: Male Reproductive System (9 decks)

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