TRH and Alzheimer disease: The study’s findings demonstrated a notable increase in FT3, FT4, TSH, and TRH levels within the brain tissues of rats in the early stages of AD, and there was a notably higher expression of TH receptors in the hippocampal tissues compared to the control group, along with FT4, TSH, and TRH were up in blood, with no change in FT3 (28).