Beyond Hormone Levels: Thyroid Hormone Signaling from Neurogenesis to Alzheimer's Disease.

Thyroid hormones (THs) critically regulate metabolism and the central nervous system (CNS) functions, acting as key factors in neuronal differentiation, synaptogenesis and myelination. Furthermore, they play a central role in regulation of cognitive process and behavior. Therefore, compromised TH signaling can interfere with normal brain function and promote neurodegenerative progression and dementia. This review explores the role of THs from embryonic development through adulthood, with particular emphasis on their crucial role in neurogenesis. We discuss key components of TH metabolism and signaling, highlighting their neuroprotective functions in maintaining cellular homeostasis. Furthermore, we address how disruptions in TH signaling contribute to cognitive decline observed in dementia with effects that are even more pronounced in Alzheimer's Disease (AD).