Fact 1: Endocrine hormones travel throughout the body in the blood.

Fact 2: Deficiencies in the Endocrine System are another source of impotence.

Given the two facts above, answer the question "Lack of what in the blood can lead to impotence? " with the following options: 
- hormones
 - hemoglobin
 - oxygen
 - iron
 - Energy.
 - t-cells
 - competition
 - Energy


 

 hormones        