THYROID HORMONE TEST #1: Urinary Thyroid Assessment

The Urinary Thyroid Assessment measures unconjugated free triiodothyronine (T3), unconjugated free thyroxine (T4) and selenium in a 24 hour urine collection. There are several reasons why a urinary thyroid assessment may be beneficial:

• A specimen collected over a 24 hour period may better reflect the average behaviour of the thyroid gland, since thyroid gland activity varies through the day. Urinary thyroid hormone levels correlate well with classical symptoms of hypothyroidism.
• Quantities of T3 and T4 in a 24 hour urine are significantly higher than those found in a spot serum sample, so levels can be more reliably measured.
• Selenium is a cofactor for 5′-deiodinase, the enzyme required to convert T4 to T3. A low 24 hour urinary selenium level likely correlates with overall selenium deficiency and decreased tissue availability of T3 due to decreased conversion of T4 to T3.

THYROID HORMONE TEST #2: Urinary Iodine and Bromine

• measures iodine, bromine and the ratio of Br to I in urine
• option to test either first morning or 24-hour urine
• assesses sufficiency of iodine intake
• assesses bromine exposure
• both raw ug/L and normalized ug/g creatine are reported
• 24-hour collection results also reported as mass/24 hours
• tested via ICP-MS technology

This test is used to ensure your iodine intake is optimal (for both the general population or specific populations such as pregnant women). North American soil contains less iodine than island countries that have more exposure to the ocean, and our populations tend to eat less seafood and sea vegetation (eg. seaweed), which are good sources of iodine, than many island nations, and consequently we have a higher incidence of thyroid disease. Adequate intake of iodine may also provide protection against breast, thyroid or prostate cancer.

Bromine is in the same element family as iodine and as such, exposure to bromine results in a decrease in the bodily stores of iodine as a result, as they compete for tissue stores. Bromine exposure can occur by way of medications, foods treated with pesticides, water purifiers and fire retardant chemicals, and can be measured through this test, helping to determine if iodine stores are or may be compromised. Also, individuals exposed to pesticides or fumigants should assess bromine excretion.

Urinary iodine levels may be used to assess appropriateness of dose and/or absorption of iodine, rather than blindly taking iodine supplements without measurements. With initiation of iodine supplementation, measuring urinary iodine levels can also be used to perform an iodine loading test.