Characteristic plasma hormone changes in Alzheimer's disease

Area of Science:

• Endocrinology
• Neuroscience
• Gerontology

Background:

• Alzheimer-type dementia (ATD) is a progressive neurodegenerative disorder.
• Endocrine system dysregulation is increasingly recognized in dementia.
• Distinguishing ATD from depression requires reliable biomarkers.

Purpose of the Study:

• To investigate and compare endocrine profiles in patients with ATD, major depressive disorder (MDD), and healthy controls.
• To identify specific hormonal markers associated with ATD.
• To evaluate the potential of these markers as diagnostic tools for Alzheimer's disease.

Main Methods:

• Systematic endocrine investigation involving blood sampling.
• Measurement of plasma concentrations of growth hormone (GH), thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), reverse triiodothyronine (rT3), and oestrogen-stimulated neurophysin (ESN).
• Comparison of hormone levels across ATD, MDD, and control groups, with stratification by sex where applicable.

Main Results:

• Plasma GH concentrations were higher in the morning in ATD compared to MDD.
• Plasma TSH concentrations were elevated throughout the day in ATD versus MDD and in female ATD versus female controls.
• Plasma ESN concentrations were lower throughout the day in ATD compared to MDD and controls, and lower in the morning in ATD compared to other dementias.
• Normal T3, T4, and rT3 levels ruled out reduced negative feedback as a cause for elevated TSH.

Conclusions:

• Elevated plasma GH and TSH in ATD may indicate reduced hypothalamic somatostatin.
• Decreased ESN concentrations in ATD suggest reduced central cholinergic activity.
• These selective hormonal alterations present a potential diagnostic biomarker for Alzheimer's disease.