I had sudden onset in teenage years mirrored that of my mother and my grandson. Initially I was misdiagnosed with mono. With thyroid, my body stabilized. Unfortunately, by moving around the United States I have had to frequently seek out new physicians. Several tried synthetics; each time with poor, life-changing results. Finally one of the doctors filed an adverse reaction to Synthroid on my behalf. I have continued to maintain in good health on Armour Thyroid for over 50 years and cringe at the thought of what withdrawal would do to my health both physically and mentally.