B. Pepsinogen. A. Vasopressin. Which of the following is an inactive form of an enzyme that is converted into an active form within the gastro-intestinal tract? A. Vasopressin. B. Pepsinogen. C. Enterokinase. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above. Which of the following substances are released from cells whose cell bodies are in the hypothalamus? A. Oxytocin. B. Vasopressin. C. GH (Growth Hormone). D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.