Possible Related Side Effects of Chronic Fatigue Syndrome

Orthostatic HypotensionOrthostatic hypotension is defined as an excessive fall in blood pressure on standing, usually greater than 20/10 mmHg. It is considered to be a manifestation of abnormal blood pressure regulation due to a variety of causes.

Hypotension, particularly orthostatic hypotension, is a common symptom in chronic fatigue patients. Many people with Chronic Fatigue Syndrome have chronic low blood pressure (the normal is 120/80 mmHg), which is made even worse on standing. This may be a particular problem in the morning, when standing can cause dizziness. Exercise or a heavy meal may exacerbate the symptoms. Syncope is a loss of consciousness and postural tone caused by diminished cerebral blood flow. Syncope often occurs during the morning shower, perhaps due to the vasodilating effect of hot water.

There are several mechanisms that govern blood pressure. Upon standing, a large amount of blood pools in the veins of the legs and trunk. The transient decrease in venous return to the heart results in a low blood pressure. The body responds with a sympathetic-mediated release of catacholamines that increase heart rate contraction and vasoconstrict the arteries. With continued standing, antidiuretic hormone (ADH) is secreted which activates the renin-angiotensin-aldosterone system, subsequently causing sodium and water retention and an expansion of the circulating blood volume.

There are many causes of orthostatic hypotension, including:

Hypovolemia (low blood volume) induced by excessive use of diuretic agents (e.g., loop diuretics, such as furosemide, bumetanide, and ethacrynic acid) and relative hypovolemia due to vasodilator therapy with nitrate preparations and calcium antagonists (verapamil, nifedipine, or diltiazem) or with angiotensin converting enzyme (ACE) inhibitors.
Histamine, a key player in allergic reactions, induces vasodilation and hypotension.
Potassium deficiency (hypokalemia) impairs the reactivity of vascular smooth muscle and may limit the increase in peripheral vascular resistance on standing
The adrenocortical hypofunction of Addison's disease may lead to orthostatic hypotension in the absence of adequate salt intake.

Several classes of drugs reversibly impair autonomic reflexes and reduce blood pressure on standing as an important adverse effect. These include many drugs used to treat psychiatric disorders such as the monoamine oxidase inhibitors (MAOIs) (isocarboxazid, phenelzine, and tranylcypromine) used to treat depression; the tricyclic antidepressants (nortriptyline, amitriptyline, desipramine, imipramine, and protriptyline) or tetracyclic antidepressants; and the phenothiazine antipsychotic drugs (chlorpromazine, promazine, and thioridazine). Other drugs that may produce orthostatic hypotension are quinidine, L-dopa, barbiturates, and alcohol.

Elevated Homocysteine LevelsHomocysteine is a sulfur-containing amino acid that is produced as a byproduct of methionine metabolism. When the body has an adequate supply of cofactors, such as vitamins B6, B12, and folic acid, homocysteine is detoxified, rendering compounds useful for other functions. Currently, homocysteine levels are in the forefront as a cardiovascular risk because of the damage that can occur to blood vessels and arteries when homocysteine levels are high.

A study of 12 women who fulfilled the criteria for both fibromyalgia and Chronic Fatigue Syndrome found that, in all the patients, the homocysteine levels were increased in the cerebrospinal fluid (CSF). There was a significant positive correlation between CSF homocysteine and B12 levels and fatigue-ability, as rated on the Comprehensive Psychopathological Rating Scale. The authors concluded that "increased homocysteine levels in the central nervous system characterize patients fulfilling the criteria for both fibromyalgia and Chronic Fatigue Syndrome ." They also noted that B12 deficiency caused a deficient remethylation of homocysteine. Therefore, a vitamin B12 deficiency can be considered a contributing factor to the higher homocysteine elevations found in these patient groups (Regland et al. 1997).

Glutathione Deficiency

Glutathione is a tripeptide made up of three amino acids: glycine, cysteine, and gamma-glutamic acid. Glutathionee functions as a modulator of cellular homeostasis, including detoxification of oxyradicals and metals. It also acts as a potent free radical scavenger that can help prevent damage to DNA and RNA, detoxify heavy metals, boost immune function, and assist the liver in detoxification through its various enzymes. Levels of intracellular Glutathione decrease with age, lowering the body's ability to detoxify free radicals and the many important enzymes Glutathione makes.

An article in the journal Medical Hypothesis proposed that Glutathione, an antioxidant essential for lymphocyte function, may be depleted in Chronic Fatigue Syndrome patients. Glutathione is needed for both the immune system and for aerobic muscular contraction. The authors proposed that Glutathione depletion by an activated immune systemalso causes the muscular fatigue and myalgia associated with Chronic Fatigue Syndrome (Bounous et al. 1999).'

Cysteine is a precursor to Glutathione. It has been hypothesized that Glutathione and cysteine metabolism may play a role in skeletal muscle wasting and muscle fatigue. The combination of abnormally low plasma cysteine and Glutathione levels, low natural killer (NK) cell activity (with a resulting susceptibility to viral infection), skeletal muscle wasting or muscle fatigue, and increased rates of urea production define a complex of abnormalities that is tentatively called "low CG syndrome." These symptoms are found in patients with HIV infection, cancer, major injuries, sepsis, Crohn's disease, ulcerative colitis, Chronic Fatigue Syndrome , and to some extent in overtrained athletes (Droge et al. 1997).

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