Any man who afflicts the human race with ideas must be prepared to see them misunderstood. ---H. L. MenckenThe Hypothalamic-Pituitary-Adrenal (HPA) axis consists of the hypothalamus, the pituitary gland, and the adrenal glands. These release adrenocorticotropic Hormone (ACTH), cortisol, epinephrine, norepinephrine, and vasopressin (Anti-Diuretic Hormone, or ADH) in response to stress. These "stress hormones" affect digestion, immune activity, emotions, sexuality, and energy expenditure. HPA axis hormones were the focus of stress research in the past because they rise sharply in response to a wide variety of stresses. However, they return to normal within hours and thus cannot explain the distant effects of stress including the pathophysiology of tissue repair and hemodynamic physiology. More recent research reveals that stress-induced MSM hyperactivity elevates thrombin generation, which energizes the release of HPA hormones. Thus, HPA axis hormones, like immune activity, are a secondary manifestation of MSM activity.