Urology>>>>>Benign Prostatic Hyperplasia (BPH) and Lower Urinary Tract Symptoms (LUTS)
Question 1#

What percentage of total serum testosterone is unbound in plasma?

A. 2%
B. 12%
C. 32%
D. 42%
E. 8%

Correct Answer is A


Answer A

Testosterone in blood is bound to strongly to SHBG and loosely to albumin. Only 1%–4% is free. Testosterone is loosely bound to albumin (and other plasma proteins) and therefore forms part of the bioavailable testosterone (BAT). Serum hormone binding globulin (SHBG) binds to 2/3 of the total testosterone. Free testosterone measures the free fraction, bioavailable testosterone includes free plus the weakly bound to albumin. Di-hydro testosterone (DHT) is the major form of androgens found within the prostate gland, the concentration is five times that of testosterone. Testosterone is converted to DHT by the action of 5 alpha reductase.