Susan Merenstein, Pharmacist/Owner
35% of the world suffers from iodine deficiency. Knowing your level is the first step to better health.
Iodine is a difficult element to get naturally in the diet, which is why much of the world has addressed iodine deficiency by fortifying foods and providing iodized salt – but iodine deficiency clearly persists in populations, including over 75 million people in the US.
Why Does Iodine Matter?
This nutritional element is essential for the synthesis of thyroid hormones. Therefore, its deficiency may contribute to hypothyroidism, goiter, pregnancy complications, and decreased IQ and cretinism in children. Even moderate deficiency has been linked with breast cancer risk and infertility.
Essential elements are abundant and only healthy when they are within optimal ranges. Iodine is paramount among these, but other important elements include copper, magnesium, selenium, and zinc – which are critical for enzymes that synthesize neurotransmitters and activate hormones.
Why Test in Urine?
A convenient way to test for iodine deficiency is to measure it in urine, since more than 90% is excreted. However, a problem with urinary iodine measurements has always been in the procedure for collecting it. With most liquid urine tests, all urine produced over 24 hours must be collected – which is logistically very difficult. Upwards of 40% of people who collect urine over 24 hours do not do it correctly and miss collections.
ZRT’s dried urine method offers a discreet, at-home testing alternative and eliminates the hassles of all-day jug urine collection. Patients collect urine on a filter strip twice during the day. Dried strips are shelf-stable for 30 days and easy to mail back to the lab for analysis.
What is the test measuring?
Dried urine is for testing elements (iodine, selenium, bromine, arsenic and mercury) that directly or indirectly impact thyroid hormone synthesis and intracellular conversion of T4 to T3. Dried urine tests have also been developed for measuring steroid hormones and their metabolites. Urine dried on filter paper produces results nearly identical to liquid urine, but has clear advantages in sample transport, size and stability compared to typical 24-hour urine collections.
Iodine and creatinine (to correct for hydration) in dried urine. Samples are collected upon waking and right before bed. We also test thyroid hormones (now including total T4) and thyroglobulin (functional marker of iodine deficiency that is elevated in iodine deficient folks) in blood spot. The iodine test measures the average of morning (this is based on a large first morning urine collection where iodine has had an opportunity to equilibrate in urine) and last night voids. These two collections compare very closely with 24 hr urine collections. The reason for doing the two at these time points is convenience for the patient, as both are collected at home.
This test will tell you where you are on the iodine sufficiency scale according to WHO and CDC. While it will tell you if your body is getting adequate iodine to manufacture thyroid hormones, it will not tell you how your thyroid gland is utilizing it to make thyroid hormones. This is why we developed the iodine/thyroid profile, which includes thyroglobulin and total T4, in addition to the other thyroid analytes we routinely test: free T4, free T3, TSH, and TPO.
Do we load first before testing?
Not recommended as stated above. This is not a loading test, which I don’t believe is accurate or meaningful because it is based on a false assumption-that all iodine will clear in 24 hr. It takes about 48 hr to get 90% of the 50 mg cleared, not 24 hr, There is no literature outside of the authors’ own self-published, non-peer reviewed work, that support the notion that the loading test is a marker of whole body sufficiency.
How much iodine does the thyroid and breasts need daily?
If you believe that the Japanese get less breast cancer because they consume more iodine, then you need to look at how much iodine they are consuming. The literature shows they are getting about 0.5-3 mg, with median of about 1-2 mg. It is NOT 12 mg, as reported by Abramson’s group. The literature is very clear on this. There are many peer reviewed papers published on this, many from
If a person is taking iodine supplementation do they go off first?
High doses can take up to 4 days to clear, and we recommend getting off before testing. Actually we don’t recommend people do anything different from what they do on a regular daily basis. We don’t recommend people do a loading dose, but just take iodine the way they do on a daily basis. This way we can see how much iodine they are getting relative to how they are feeling and how it effects their thyroid hormones (assuming they measure iodine along with thyroid hormones-recommended). This is the same idea with taking hormones. If you take a hormone every day for months/years, and go off of the hormone before testing it has no relevance to what your daily hormone levels are. Same with iodine, and how it affects your thyroid glands ability to manufacture thyroid hormones.
Why test over 24 hours if you know the body takes 48 hours to get rid of the iodine taken?
As I mentioned above, we don’t believe in any test where everyone fails nearly all the time, which is the case for the loading test. It is a test flawed in its assumptions, that 90% of a 50 mg iodine supplement will pass into urine in 24 hr. It will in about 48 hr.
ref: David Zava - Founder, CEO, and Chief Scientist | ZRT