MR Brain Spectroscopy Detects Damage In The Hippocampus Of Patients Exposed To Excess Cortisol
Cushing's syndrome is an endocrine disease causing an overproduction of the stress hormone cortisol. Surgery and medical treatment can normalise cortisol levels, however recently it has been shown that "biochemically cured" patients continue to have memory problems. Now for the first time a group of researchers from the Sant Pau Hospital in Barcelona has scanned the brains of patients who had suffered from Cushing's syndrome and found that they exhibit changed levels of brain metabolites, which are associated with memory and cognitive impairments. This finding may also have clinical implications for otherwise healthy patients who take high levels of glucocorticoid drugs for inflammatory, rheumatoid diseases, allergies and probably everyday chronic stress.
Cortisol (a glucocorticoid hormone), is naturally produced by the adrenal glands in response to stress. Long term exposure to high levels of cortisol is known to be associated with a range of cognitive impairments - this is true for Cushing's syndrome patients, and probably would be also for those who take glucocorticoid drugs.
Eugenia Resmini and colleagues, working at the Centre for Biomedical Research on Rare Diseases (CIBERER), Sant Pau hospital in Barcelona, used proton magnetic resonance spectroscopy to measure a series of metabolites in the hippocampus of the brains of 18 patients who had been treated for Cushing's syndrome, and compared these results to 18 healthy control subjects. They found that levels of the metabolite NAA (NAcetyl-aspartate) were significantly lower in the Cushing's patients, indicating neural dysfunction, whereas Glx (Glutamate +Glutamine) levels were higher, suggesting that glial cells were proliferating as a repair mechanism.
According to Dr Resmini MD, PhD, Endocrinologist at the Centre for Biomedical Research on Rare Diseases (CIBERER), Hospital de Sant Pau, Barcelona, Spain:
"Patients with Cushing's syndrome are exposed to abnormally high levels of glucocorticoids, which is associated with a wide range of cognitive impairments, as well as loss of brain volume. We studied the hippocampus, which is a critical area for learning and memory and, as it is rich in glucocorticoid receptors, is especially vulnerable to glucocorticoid overexposure. Cushing's syndrome patients with severe memory impairment are known to have a smaller hippocampus. We have now found abnormal levels of metabolites in the hippocampi of Cushing's patients with normal hippocampal volumes, indicating that these are early markers of glucocorticoid neurotoxicity, which would precede hippocampal volume reduction.
"Identifying these metabolites as a marker would be a way of allowing earlier diagnosis and treatment of cognitive impairments. This may also allow us to monitor patients taking glucocorticoid drugs, which have potentially damaging side effects. On the other hand, the fact that these markers are still present in Cushing's patients after being "biochemically cured", may show that once cognition has been damaged in Cushing's syndrome, it may not be fully reversible. For this reason an earlier diagnosis of the disease and a rapid normalization of hypercortisolism would avoid the progression of hippocampal damage and of memory problems".