W3006  Physiology      Fall 2002   Problem set #2  -  Male reproductive system

 

1   Cells that secrete Androgen Binding Protein also
A. secrete FSH    B. secrete LH    C. secrete testosterone D. secrete inhibin   E. support developing spermatozoa    F.  form tight junctions with each other 

2.   Inhibinís role is to inhibit the secretion of   _____________________.

3.  Prostaglandins in the semen come mostly from the
A. prostate gland       B.  seminal vesicles         C.  Sertoli cells    D. bulbourethral glands     E.  vas (ductus) deferens

4.  The pituitary gland is removed from a rat.   What changes would you expect to see in:  (just write:  increase, decrease or no change)

A.  Blood levels of GnRH
B.  Blood levels of LH
C.  Blood levels of testosterone
D.  Spermatogenesis

5.      A man is found to have elevated plasma FSH, normal LH, normal T, and atrophied seminiferous tubules.  Explain what the probable defect is.

6. When Mark McGwire established his home-run record, there was much talk about his use of "Andro", technically known as androstenedione, or ASD, one of the androgens naturally produced by the testes.  The Endocrine Society put out a press release describing how taking too much Andro can "shrink your grapes to raisins".  Why might ASD be able to cause the testes to become smaller?  Your answer should include an explanation of how testes size is normally maintained, and where ASD might be having an effect.

 

Answers

1.   D. secrete inhibin   E. support developing spermatozoa    F.  form tight junctions with each other  Sertoli cells do all these things

2..  FSH

3.  B.  seminal vesicles

4. A.  Blood levels of GnRH increase due to less negative feedback, since decreased testosterone
B.  Blood levels of LH decrease decrease in the pituitary
C.  Blood levels of testosterone decrease since less LH stimulation
D.  Spermatogenesis  decrease since less FSH and less testosterone

5.     Since LH is normal, the hypothalamus and GnRH must be okay.  Problem is either that the Sertoli cells can't respond to FSH (e.g., no receptors), or they don't produce enough inhibin.  (In fact, the latter has been shown to occur in some such men.)

6.  Normally testes size is maintained by gonadotropins; see textbook for flowchart.  Testosterone has negative feedback effects on anterior pituitary, causing a decrease in gonadotropins, which would then lead to a decrease in T.  So ASD acts like T at the hypothalamus, anterior pituitary, causing a decrease in gonadotropins and a decrease in endogenous T secretion.  (It doesn't have strong enough effects on the testes, so effect there is less than the normal T)