Cerebrospinal fluid levels of hypothalamic-pituitary-adrenal axis hormones in MCI and dementia due to Alzheimer's disease: a systematic review.

Underlying the neuropsychological manifestations of Alzheimer's disease (AD), hypothalamic-pituitary-adrenal (HPA) axis dysregulation and subsequent hypercortisolemia have been proposed as major mechanisms driving AD progression from mild cognitive impairment (MCI) to the onset of dementia. Nonetheless, changes in cerebrospinal fluid (CSF) levels of HPA axis hormones remain controversial despite their potential in AD diagnosis and prognosis testing. Objective: This study aimed to review the evidence of the variation in CSF levels of CRH, ACTH, and cortisol in subjects with mild cognitive impairment (MCI) and AD compared with subjects without cognitive disorders. Methods: A systematic review was conducted in MEDLINE, EMBASE, and Web of Science databases on July 5, 2022. Results: Seventeen observational studies were included. The results from the compiled investigations showed that individuals with AD exhibit a significant elevation of CSF cortisol levels which appear to correlate with the presence of the ApoE-ε4 allele, being higher in those homozygous for this allele. The variation of CSF CRH and ACTH levels in AD, on the other hand, is still inconclusive. Moreover, most studies found no significant difference in CSF cortisol levels in individuals with MCI compared to healthy subjects and patients with AD. Conclusion: The findings gathered in this review disclose a significant elevation of CSF cortisol levels in AD. Future investigations are warranted to elucidate the potential use of CSF cortisol as a biomarker in AD-associated dementia.