A method for prevention of Alzheimers Disease (AD) is presented. The principal cause of AD is a deficiency at the cellular level of the human brain, of the effects of the active form of thyroid hormone, tri-iodothyronine (T3). Lifelong T3 replacement, beginning in early to mid life and, in some cases later, overcomes these blocks to T3 production and actions and prevents AD in a majority of the sub-types of AD.
