The zona fasciculata chiefly produces glucocorticoids (mainly cortisol in the human), which regulates the metabolism of glucose, especially in times of stress (., part of the fight-or-flight response ), it is stimulated by the hormone Adrenocorticotropic Hormone (ACTH) which is released from the anterior portion of the pituitary and axised upon this adrenal gland. This tissue also generates a small amount of weak androgens (., dehydroepiandrosterone ). The main source of androgens will come from the zona reticularis region. In certain animals such as rodents , the lack of 17alpha-hydroxylase results in the synthesis of corticosterone instead of cortisol.
However, contrary to what one is apt to read in anti-evolutionary literature, there is currently no evidence demonstrating that the appendix, as a separate organ, has a specific immune function in humans ( Judge and Lichtenstein 2001 ; Dasso et al. 2000 ; Williams and Myers 1994 , pp. 5, 26-29). To date, all experimental studies of the function of an appendix (other than routine human appendectomies) have been exclusively in rabbits and, to a lesser extent, rodents. Currently it is unclear whether the lymphoid tissue in the human appendix performs any specialized function apart from the much larger amount of lymphatic tissue already distributed throughout the gut. Most importantly with regard to vestigiality, there is no evidence from any mammal suggesting that the hominoid vermiform appendix performs functions above and beyond those of the lymphoid-rich caeca of other primates and mammals that lack distinct appendixes.