Stand alone lab results when within range actually mean very little. Ranges are derived from mass samplings and your an individual. A couple tenths of a point in T3 can mean a world of difference in how one feels even if both numbers are "in range". Ideally one should compare their own labs to their own historical data to see how things have changed, comparing yourself to 100,000 others isnt very valuable.
If all your taking is D3 and Iodine you need to consider that your likely deficient in many nutrients. Most need others to work properly and when used in their absence can actually cause problems.
For example Iodine without ample selenium can actually cause problems and also the reverse. D3 without the other fat soluable vits and K can also have adverse effects.