Multiple choice Gastric acid output is influenced by all the following hormones except parathormone thyroxin both (1) and (2) neither (1) nor (2) Reveal answer Fill a bubble to check yourself A Correct answer Explanation Gastric acid secretion is regulated by gastrin, histamine, and acetylcholine. Thyroxin can influence metabolic rates and indirectly affect secretion, but parathormone is not a primary regulator of gastric acid output.