What is the most likely cause of his sterility?

Question

A man who was sterile was found to have normal plasma concentrations of testosterone and LH, but an increased plasma concentration of FSH. Male secondary sex characteristics were normal. What is the most likely cause of his sterility?
a. deficient secretion of GnRH
b. deficient secretion of LH
c. abnormal function of Leydig cells
d. abnormal function of Sertoli cells
e. inflammation of the prostate gland

Answer 1

D. abnormal function of sertoli cell.
FSH acts on Sertoli cells in a negative feedback loop. If it doesn't get that feedback, it will increase production of FSH in an effort to achieve it. So, the Sertoli cells are not responding as they should.