A recent PubMed article talks about the serotonin system being over-active in CFS patients. It states that genetic abnormalities were found in serotonin receptors of patients. They were all located in the same receptor subtype (5-HT receptor subtype HTR2A).
Another article dated 2001, says that researchers found evidence of increased serotonergic activity and elevated levels of a serotonin metabolites in patients. It also says that certain treatments that increased serotonin turnover rates, like NADH, led to an improvement in symptoms.
I was wondering if there was a connection between the overactive serotonin system and the HPA axis.
I know that in people that are depressed, there is chronic overactivity of the HPA axis (in most cases). This increase in HPA activity leads to a decrease in the activity of serotonin. In CFS, it seems to be complete opposite.
Maybe the reduced activity of the HPA axis leads to an oversensitivity of serotonin receptors, or vice versa. But which is the cause and which is the symptom?
Also there is some evidence that the immune system, the serotonin system, and the HPA axis may all be interacting with each other.
Could a viral infection kick off the disease by interacting with the immune system, which then could effect the serotonin levels and the HPA axis?
Could a malfunctioning HPA axis lead to increased serotonin activity and decreased immunity? Causing viruses to re-emerge and cause symptoms of CFS.
This could explain why so many causes are implicated in CFS. The interaction and balances of these systems can be disrupted in many different ways. It would be incredibly difficult for a doctor to find the root cause.
In the CDC’s genetic studies of CFS, there was found to be malfunctioning genes on the glucocorticoid receptor, the serotonin [receptor], and tryptophan hydroxylase.
The glucocorticoid receptor senses how much cortisol is in the body and is part of a feedback loop that helps the body determine how much cortisol to produce.
Tryptophan Hydroxylase directly controls the levels of serotonin in the boy, and the serotonin receptors control how the body interacts with the serotonin.
Just thinking about how these complicated systems interact, it is easy to see why CFS symptoms vary so greatly between patients. And how many different causes can bring about the same disease.