An endogenous chemical agent of the disease is 

An endogenous chemical agent of the disease is uric acid.

Endogenous chemical agents are those that are produced within the organism, tissue, or cell. Intrinsic or internal variables impacting human health refer to endogenous chemical substances and genetic mutations. Organic or metabolic disorders are diseases induced by intrinsic causes. Endogenous chemicals include urea, uric acid, hormones, and enzymes. Uric acid is created in the human body, and if it is not cleared by the kidneys, it can lead to gout, a dangerous condition caused by the accumulation of uric acid in joints.

As a result, the correct answer is A.