Final answer:
The hormone or enzyme involved in fluid balance and produced by the kidneys is antidiuretic hormone (ADH).
Step-by-step explanation:
The hormone or enzyme involved in fluid balance and produced by the kidneys is antidiuretic hormone (ADH).
The antidiuretic hormone (ADH), also known as vasopressin, is a peptide hormone that plays a crucial role in regulating water balance in the body. Produced by the hypothalamus and released by the pituitary gland, ADH acts on the kidneys to control the amount of water reabsorbed into the bloodstream and the concentration of urine.