The Unreliable TSH Lab Test

(original article here.)

Suzy is a 59 year old post menopausal woman with low thyroid function.  About three months ago, she started her bio-identical hormone program which included natural thyroid pills.  After starting the program, she was doing well with more energy, better sleep, improved appearance of skin and hair, and resolution of her menopausal symptoms of flashes and sweats.

A New Set Of Thyroid Labs

However about 12 weeks into her program, Suzy had a visit with her primary care doctor who did a follow up thyroid panel.  Her primary care doctor  informed Suzy that her TSH test result was outside of the normal range, and therefore, her thyroid dose was too high, and should be reduced. (Note TSH stands for Thyroid Stimulating Hormone and is made by the pituitary gland)

I explained to Suzy that her primary care doctor was incorrect in relying slavishly on the TSH test. Even though her TSH test was 0.15 which is below the lab reference range of .3, this was perfectly acceptable and indicated her thyroid medicine was suppressing the TSH to a low level which was perfectly fine.

No Clinical Evidence of Thyrotoxicosis

I also informed Suzy that her Primary Care Doctor is mistakenly relying on the TSH test to determine her thyroid dosage. The TSH test is an indirect measure of thyroid function and can be unreliable. A more accurate indicator of thyroid function is the free T3, which in her case was 375, well within the normal range of 240 to 420. The Free T3 lab test together with the absence of any signs or symptoms of thyroid excess indicates she is using the correct dosage of natural thyroid medication. Symptoms of thyroid excess are rapid heart beat or palpitations, and Suzy reported no such symptoms. In fact, Suzy said she felt fine and now that she understands it, she didn't want to go back to the way she was feeling before she started the thyroid pills.

This scenario is repeated about once a week at my office.

Conventional Docs Slavishly Rely on the TSH

Conventional primary care doctors use a different lab panel from mine. They never do a Free T3 test which is the most informative thyroid lab test, and instead rely on the TSH which is not a direct measure of thyroid function and can in fact be unreliable. Most conventional doctors are unfamiliar with the use of natural thyroid which contains both T3 and T4, and instead use Synthroid which is quite different, containing only T4. 

No Time for Explanations

Since the Primary care doctors bill the health insurance for the office visit and payment is only a few dollars, the office visit is brief, 3-5 minutes.  In this short time, Primary care doctors can provide only the most basic care, which is a quick look at the TSH lab test.  If the TSH is below the lab reference range the doctor gives a new prescription for Synthroid with a reduced dosage.  If the TSH is above the reference range, the primary care doctor will increase the Synthroid dosage.

The Cleveland Clinic Chimes In

A few months ago, I found myself talking on the phone with an endocrinologist at the Cleveland Clinic explaining why the TSH blood test can be unreliable. He informed me I was wrong, and that he uses the TSH test as the gold standard. We agreed to disagree and parted company as friends. I have found that, in general, endocrinologists and mainstream doctors rely heavily on TSH to make a diagnosis of low thyroid.

Why Thyroid Blood Testing is Unreliable.

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