Posted by Elroy on June 21, 2005, at 18:19:37
In reply to Re: HPA Axis Anti-Cortisol Therapy - MORE INFO 2 » Elroy, posted by Elroy on June 21, 2005, at 18:13:48
Another VG explanation site...
http://dr-john.ca/depression_article13.php
A. The HPA Axis
This axis (hypothalamic-pituitary-adrenal axis) includes (a) the limbic system and pre-frontal cortex and (b) the neuro-endocrine system as described below. In response to a number of things including a current stressor, a chronic stressor, and stimuli or memories associated with a previous stressor, the HPA axis is activated.* The Limbic System Some major biological processes of motivation, emotion, and drive (including eating, drinking, sexual desbire, energy, emotional memory, and mood) are governed in part by an inter-related group of brain structures including the hypothalamus, the hippocampus, the amygdala, the pituitary gland, the thalamus, the locus coreleus, and parts of the pre-frontal cortex. Together, these structures are known as the limbic system. Disruption of any part of this system can lead directly to symptoms we associate with depression as well as having an impact on neuro-transmitters and the neuro-endocrine system.
* The Neuro-Endocrine System This system consists of a number of interconnected sub-systems including the limbic system which produce a large number of chemicals called hormones. Among them are CRF, ACTH, cortisol (from the hypothalamic-pituitary-adrenal system {the HPA axis}), TSH (from the hypothalamic-pituitary-thyroid system), melatonin, (from the pineal gland), and both estrogen and progesterone (from the female reproductive system). These chemicals are released into the blood stream and have very rapid effects on such things as blood glucose level, metabolic rate, nervous system tone, sex, sleep-wake cycle, regulation of the immune system, and certain aspects of emotion, and attention. Additionally, the HPA axis is linked to the neurotransmitters serotonin and nor-epinepherine. Thus, short-term activation of this system is associated with symptoms of anxiety or over-arousal while there is an association between prolonged activation or insufficient nervous system variability (sometimes referred to as vagal tone and measured as heart rate variability) and symptoms of depression and post-traumatic stress disorder as well as increases in the risk for high blood pressure, heart disease, and possibly auto-immune diseases. For example, 20% to 40% of outpatients with depression and 60% to 80% inpatients with depression have one or more signs of increased neuro-endocrine activation. Also, 50% to 70% of those with Cushing's Disease (a disorder of the adrenal gland) also have depression which often precedes other symptoms of the disease. Moreover, there is evidence suggesting that anti-depressant medication can normalize the HPA axis via effects on serotonin. Laboratory tests are available to assess the functioning of the neuro-endocrine system.B. Stressors
Stressors activate the HPA Axis so our bodies have the capacity to respond. Then, generally once the stressor is over, gradually the HPA Axis returns to normal. However, for a variety of reasons (for example, too many stressors, too severe in intensity, and too long in duration) sometimes the HPA Axis stays activated for a long time which ultimately leads to depletion of neuro-transmitters such as nor-epinephrine with the resulting symptoms of depression. There are many different types of stressors and I have identified a number of them below....Elroy
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poster:Elroy
thread:515432
URL: http://www.dr-bob.org/babble/20050617/msgs/516743.html