 Perhaps more threatening to the whole-brain approach is the growing empirical evidence that total brain failure is not sufficient for human death —assuming the latter is construed, as whole-brain advocates generally construe it, as the breakdown of integrated organismic functioning mediated by the brain. Many of our integrative functions, according to the challenge, are not mediated by the brain and can therefore persist in individuals who meet whole-brain criteria for death by standard clinical tests. Such somatically integrating functions include homeostasis, assimilation of nutrients, detoxification and recycling of cellular wastes, elimination, wound healing, fighting of infections, and cardiovascular and hormonal stress responses to unanesthetized incisions (for organ procurement); in a few cases, brain-dead bodies have even gestated a fetus, matured sexually, or grown in size (Shewmon 2001; Potts 2001). It has been argued that most brain functions commonly cited as integrative merely sustain an existing functional integration, suggesting that the brain is more an enhancer than an indispensable integrator of bodily functions (Shewmon 2001). Moreover, several studies have demonstrated that most patients diagnosed as brain dead continue to exhibit some brain functions including the regulated secretion of vasopressin, a hormone critical to maintaining a body's balance of salt and fluid (Halevy 2001). This hormonal regulation is a brain function that represents an integrated function of the organism as a whole (Miller and Truog 2010).