The primary means of HPA axis regulation occurs through a well characterized negative feedback loop in which glucocorticoids suppress ongoing HPA axis activity at both the hypothalamic and pituitary level (Pecoraro et al., 2006). However, HPA axis regulation is more complex than a thermostat model in which circulating glucocorticoids dictate the steady state activity of the HPA axis. For example, in the absence of glucocorticoids (following adrenalectomy), consumption of sucrose can normalize increased CRH expression and ACTH secretion (Laugero et al., 2001) indicating the presence of mechanisms of HPA axis regulation beyond glucocorticoid negative feedback.
