Testosterone is the key hormone produced by the Leydig cells of the  testicles and is responsible for the normal growth and development of  male organs and for maintenance of other sexual characteristics. Aside  from sexuality, it also contributes to some essential body functions  such as embryological development, facial hair development, brain  function, body muscle mass, bone strength, red blood cells function and  even mood and energy levels.

The range for normal testosterone  level is 300 -1100 (ng/dL). It is optimal for a man to get around 800 –  1100 (ng/dL). When a man reaches his mid 30’s, production of  testosterone declines an estimate of 1% each year – 10% in 10 years or  even more. Greater decline in testosterone level can happen due to  obesity, infectious diseases, excess of blood iron and inflammatory diseases.