Scientists in Australia believe they've figured out a potential cause of chronic fatigue syndrome -- a debilitating condition so mysterious, some doctors doubt it even exists.
Also known as myalgic encephalomyelitis, people suffering from chronic fatigue syndrome (CFS) report:
There is no known cause, but scientists at Griffith University in Queensland have found a promising lead in immune cells.
They've found a lack of TRPM3 receptors in the cells of CFS patients.
"These receptors are important as they move calcium inside the cell," says study leader Prof Sonya Marshall-Gradisnik.
"Interestingly in this study we also reported a significant reduction of calcium inside these cells from CFS/ME patients."
She says the discovery shows a "potentially key contributing factor" contributing to CFS.
"We are now much closer to having a complete understanding of CFS."
Current treatments for CFS largely focus on treating the symptoms, such as using anti-inflammatory painkillers. Cognitive behavioural therapy has also been shown to help sufferers cope, as has light, regular exercise.
Other recent research has pointed towards viral infection as the root cause of CFS, but there's still no solid proof that is the case.
The new research was published in journal Biological Research.