# HPA axis and stress



## trbell (Nov 1, 2000)

good overviewarticle:Hypothalamic-pituitary-adrenal axis, neuroendocrine factors and stress.Journal: J Psychosom Res 2002 Oct;53(4):865Authors: Tsigos C, Chrousos G.Affiliation: Hellenic National Diabetes Center, Athens, GreeceNLM Citation: PMID: 12377295The stress system coordinates the adaptive responses of the organism tostressors of any kind.(1) The main components of the stress system arethe corticotropin-releasing hormone (CRH) and locusceruleus-norepinephrine (LC/NE)-autonomic systems and their peripheraleffectors, the pituitary-adrenal axis, and the limbs of the autonomicsystem.Activation of the stress system leads to behavioral and peripheralchanges that improve the ability of the organism to adjust homeostasisand increase its chances for survival. The CRH and LC/NE systemsstimulate arousal and attention, as well as the mesocorticolimbicdopaminergic system, which is involved in anticipatory and rewardphenomena, and the hypothalamic beta-endorphin system, which suppressespain sensation and, hence, increases analgesia. CRH inhibits appetite andactivates thermogenesis via the catecholaminergic system. Also,reciprocal interactions exist between the amygdala and the hippocampusand the stress system, which stimulates these elements and is regulatedby them. CRH plays an important role in inhibiting GnRH secretion duringstress, while, via somatostatin, it also inhibits GH, TRH and TSHsecretion, suppressing, thus, the reproductive, growth and thyroidfunctions. Interestingly, all three of these functions receive and dependon positive catecholaminergic input.The end-hormones of the hypothalamic-pituitary-adrenal (HPA) axis,glucocorticoids, on the other hand, have multiple roles. Theysimultaneously inhibit the CRH, LC/NE and beta-endorphin systems andstimulate the mesocorticolimbic dopaminergic system and the CRHpeptidergic central nucleus of the amygdala. In addition, they directlyinhibit pituitary gonadotropin, GH and TSH secretion, render the targettissues of sex steroids and growth factors resistant to these substancesand suppress the 5' deiodinase, which converts the relatively inactivetetraiodothyronine (T(4)) to triiodothyronine (T(3)), contributingfurther to the suppression of reproductive, growth and thyroid functions.They also have direct as well as insulin-mediated effects on adiposetissue, ultimately promoting visceral adiposity, insulin resistance,dyslipidemia and hypertension (metabolic syndrome X) and direct effectson the bone, causing "low turnover" osteoporosis.Central CRH, via glucocorticoids and catecholamines, inhibits theinflammatory reaction, while directly secreted by peripheral nerves CRHstimulates local inflammation (immune CRH). CRH antagonists may be usefulin human pathologic states, such as melancholic depression and chronicanxiety, associated with chronic hyperactivity of the stress system,along with predictable behavioral, neuroendocrine, metabolic and immunechanges, based on the interrelations outlined above.Conversely, potentiators of CRH secretion/action may be useful to treatatypical depression, postpartum depression and the fibromyalgia/chronicfatigue syndromes, all characterized by low HPA axis and LC/NE activity,fatigue, depressive symptomatology, hyperalgesia and increasedimmune/inflammatory responses to stimuli. --------------------------------------------- Too much mail? Try a digest version. See http://www.co-cure.org/digest.htm Send posts to mailto:CO-CURE###listserv.nodak.edu Join or leave the list at http://www.co-cure.org/sub.htm ---------------------------------------------tom


----------

