Inhibin & Testosterone

Summary

Inhibin is produced in the testes and other locations. It reduces sperm production, the production of FSH from the pituitary, however, it also reduces LH. It is possible inhibin production is suppressed by potassium, which may be the reason why potassium deficiency leads to such dramatic drops in testosterone production in animal models. It is also possible that inhibin is excessively produced when the prostate is enlarged or inflamed.

Studies

Inhibin B is produced in the testis, principally by the Sertoli cells.
https://www.ncbi.nlm.nih.gov/pubmed/15319820

In the case of benign prostatic hypertrophy, there was a significant rise in inhibin levels as compared to age-matched control groups, whereas LH and FSH levels were decreased significantly.
http://onlinelibrary.wiley.com/doi/10.1002/pros.2990100203/abstract

Rat ventral prostate as an independent source of inhibin-like material
http://www-old.ias.ac.in/jarch/jbiosci/14/69-78.pdf

Biosynthesis and localization of inhibin in human prostate
http://onlinelibrary.wiley.com/doi/10.1002/pros.2990100107/abstract

Serum and urinary prostatic inhibin-like peptide in benign prostatic hyperplasia and carcinoma of prostate.
https://www.ncbi.nlm.nih.gov/pubmed/2462465
Prostatic inhibin-like peptide (PIP) in the serum was significantly elevated serum PIP levels in benign prostatic hypertrophy.

Serum inhibin—not a cause of low testosterone levels in hypogonadal prostate cancer?
https://www.ncbi.nlm.nih.gov/pubmed/18407338