Diagnosed hypothyroidism 4yrs ago.tsh was 6.5.on synthroid 50 mcg.now tsh over 1.no antibodies detected.is it autoimmune or not?catch cold frequently

Likely autoimmune: Most cases of hypothyroidism are due to autoimmune thyroiditis. Antibodies may decline as the thyroid tissue is lost to the inflammation. Frequent colds may not be related to thyroid but could be due to Dexamethasone. Do take Flu vaccine. Wish you good health! - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex. Get HPV vaccine

Unlikely: Autoimmune thyroid problem is usually diagnosed based on the presence of anti-thyroid antibodies. In the absence of those, one cannot be sure that the mechanism is of autoimmune origin. Allergy is more likely the cause for frequent cold symptoms and thus consider seeing an allergist to find out what may be the cause.