Thyroid Testing – Optimal Levels

Last week I spoke to an audience of 250 at the Natur-Tyme Health Fair in Syracuse, New York. A question came up about thyroid testing and I promised this very lovely woman that my next blog would be dedicated to the discussion of optimal thyroid hormone testing.

The thyroid is a vitally important hormonal gland that plays an essential role in metabolism, growth and energy levels.

An estimated 27 million Americans have thyroid disease, and about 13 million of them are undiagnosed!

The diagnosis of hypothyroid or low thyroid is based on symptoms and the results of blood tests that measure the levels of TSH (thyroid stimulating hormone), free T3 (triiodothyronine), free T4 (thyroxine), reverse T3, thyroid antimicrosomal antibodies (TPO Abs) and antithyroglobulin antibodies Tg Abs).

Commonly TSH is the only blood test ordered by most medical doctors, and thyroid function is considered “normal” is the TSH falls between 0.35 – 5.5 IU/ml. However, naturopathic doctors and some medical doctors are using a new “norm” for the TSH lab value and will treat for hypothyroidism if the TSH lab value is above 1.5 - 2.0, especially with accompanying low thyroid symptoms. Although many medical doctors will only test TSH, it is important to measure the levels of actual thyroid hormones (T4 and T3) to get a more accurate picture of the function of the thyroid.

TSH alone and the old lab reference range are often inadequate and many hypothyroid patients suffer needlessly for years.

Most labs also routinely measure TOTAL circulating T3 and T4, which are largely protein-bound but not necessarily available for metabolic activity. Free T3 and T4 are more available for tissue receptors and provide a more accurate measurement for thyroid function.

So, without further ado and in honour of my lovely audience member from Syracuse, the reference ranges for free T3 are:

80-230 ng/dL (US) and 1.23-3.53 nmol/L (standard international units)

OPTIMAL RANGES for free T3 are:

100-230 ng/dL (US) and 1.54 – 3.53 nmol/L (standard international units)

The reference ranges for free T4 are:

4.8 – 13.2 mcg/dL (US) and 61.8 – 169.9 nmol/L (standard international units)

OPTIMAL RANGES for free T4 are:

6.0 – 12.0 mcg/dL (US) and 77.2 – 154.4 nmol/L (standard international units)

 ***I realize that some labs in the US and around the world use different units and reference ranges so please check that the units correspond to the above ranges.