Peak, I use Mercola's iodine supplement a few times per week. I first encountered low iodine readings when I was working at ZRT Laboratory over 10 years ago. My urine test was low (70 on 100-1100 scale). I have been cold susceptible my entire life; however, I noticed that after I started taking iodine that my cold resistance is much better now. I can go snowboarding, or swimming in cold water, and not feel like I'm going to freeze to death. My follow-up urine tests showed normal iodine readings (402 on 100-1100 scale), and my hair tests also show mid-range iodine. This has remained mostly consistent for about 10 years now. I initially tried the trifecta (tyrosine, selenium, iodine) but the negative effects of the tyrosine made me stop. I did however return to iodine, and eventually selenium based on my results. Interestingly, the only part of my thyroid profile that changed was my TSH went up from 0.5-1.0 to 1.5-2.0 range. No other part of my thyroid serum profile changed very much. As a result, I don't see much use (for me) in the thyroid serum profile testing outside of TSH. I rely on it as a piece of data, but only in conjunction with Spectracell and the hair testing.