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12 Cards in this Set

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In primary (testicular) hypogonadism, what is the more likely cause?
MORE LIKELY damage to seminiferous tubules than to Leydig cells.

Think chromosomal abnormalities...47XXY = Klinefelters

However, could be ABNORMALITY in testosterone biosynthesis in Leydig cells.
What are other causes for primary hypogonadism in men.
1) Chrosomal abnormalities like Klinefelters... seminiferous tubules damaged. Damage to Leydig variable.

2) Cryptorchidism (undescended testes)... greater abnormalities if BILATERAL. 100% of BILATERAL individuals have reduced sperm counts (33% of UNILATERALS). LOW TESTOSTERONE TOO.

3) FSH / LH receptor abnormalities.
Is it possible to acquire primary hypogonadism?
YES!

Infection --> Mumps (must have affected testes).

Chemo --> ALKYLATING AGENTS.

95% of cases are IDIOPATHIC
What are TWO TYPES of secondary hypogonadism?
CONGENITAL and ACQUIRED.

Congenital:

Hypothalamic Hypogonadism (KALLMAN'S SYNDROME)
Idiopathic Hypogonadotropic hypogonadism...no LH pulses.
3) End Organ Androgen Resistance...receptor abnormality can be total or partial. 5a-reductase abnormality.

ACQUIRED

1) Benign tumors
2) Infections (TB/meningitis)

KNOW TB and MUMPS bad for hypogonadism
What is mechanism of action behind KALLMAN'S SYNDROME (hypothalamic hypogonadism)?
Migratory failure of GnRH-producing cells from olfactory placode to hypothalamus.
How do you determine if hypogonadism problem lies in hypothalamus?
Give exogenous GnRH. SHOULD SEE LH SPIKES WITH EXOGENOUS GnRH.
What is DHT?
An androgen with 30x greater affinity for androgen receptor than testosterone.

Responsible for development of male gender specific characteristics (facial hair and deepening of the voice).

Formed from testosterone via 5a-reductase.

DHT is highly expressed in BPH
What is testosterone's role in the following body parts?

Skin? Muscle? Sex organs? Brain? Bone? Bone marrow?
Skin: Hair growth and balding

Brain: Libido

Sex Organs: Spermatogenesis, Penile growth. Prostatic growth and function.

Bone Marrow: Erythropoeisis (DIRECT FROM TESTOSTERONE)

Bone: Closure of epiphyseal. Increased density.

Muscle: Increase in lean muscle. DIRECT FROM TESTOSTERONE.
How does testosterone function as 3 hormones?
1) Direct binding to androgen receptor

2) Conversion to DHT via 5a-reductase which binds with GREATER AFFINITY to androgen receptor.

3) Conversion of testosterone to estradiol (Aromatase)
Does hypogonadism have different physiologic effects depending on when hypogonadism occurs?
YES!

In utero, first trimester...no male differentiation.

In utero, third trimester...microphallus, crytorchidism

Prepuberty: Longer legs (epiphyseal plates don't close)

Puberty: Regression of pubertal changes.
How can you use LH/FSH levels to determine if problem is PRIMARY or SECONDARY HYPOGONADISM?
If LH/FSH levels are high, then the problem should be downstream of LH/FSH production. LH/FSH is increased because of blockage. THINK PRIMARY.

If FSH/LH levels are low, then something is wrong upstream or at Anterior Pituitary...
THINK SECONDARY.
What is the biggest difference in testosterone levels between young and old men.
Spike in testosterone from about midnight to 8 AM. Levels are more similar throughout the day.