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Evaluating Normal Ranges, Ratios, TSH And Thyroid Tests

Dr. Joseph . Collins, RN, ND
Thyroid Nation

Ideal Group of Thyroid Tests

When assessing thyroid function, it is critical that the tests be done properly. Incomplete tests can result in making decisions that are based on incomplete information. The following is a list of lab tests that will completely evaluate thyroid function. Doing only part of these tests provides only part of the information. Once we all understand what each test is telling us, and why it is important, there should be no problem getting these tests done.

So, when you are concerned about thyroid function, my advice is to ask your doctor to completely evaluate your thyroid function with this group of tests.

Lab Tests to Properly Evaluate Thyroid Function

  • TSH (thyroid stimulating hormone)
  • Free T4 or Total T4 (thyroxine)
  • Free T3 or Total T3 (triiodothyronine)
  • Reverse T3 (reverse triiodothyronine)
  • Anti-thyroid peroxidase antibodies (anti-TPO)
  • Anti-thyroglobulin antibodies (anti-TG)

Collectively, these tests measure:

Hypothalamic-Pituitary-Thyroid Axis(TSH)
Thyrocyte & Thyroid Gland Health  (anti-TPO * anti-TG antibodies)
Thyroid hormone Conversion          (T4, T3 & reverse T3)

Look Beyond “Normal”

When interpreting thyroid tests, having values “within normal range” is not enough to state with any certainty that thyroid function is healthy. The trend in diagnostic medicine is to do more in-depth analysis, which typically includes evaluation of the data with percentile analysis, optimal reference ranges, and ratio analysis.


Percentile Analysis & Quartile Analysis

Percentile analysis gives an objective quantitative presentation about how healthy a person is based on where the lab test is within the reference range. For example if a free T3 levels are 2.8 and the normal range is 2.3 to 5.0, it is obvious that the patient is “within normal range”. However, the patient has multiple symptoms of hypothyroid function. Is normal the same as “ideal”?
The math is quite simple:
  • Percentile Analysis = (PV-LR) / (HR-LR) x 100
  • PV = Patient Value
  • LR = Low Reference Range
  • HR = High Reference Range
Doing the math we get:
(2.8-2.3) /(5.0-2.3) x 100 = 18
So, this patient’s free T3 is at the 18th percentile. Since this is below the 30th percentile, it may be considered “subclinical hypothyroidism”, not low enough to be called a full-blown disease, but low enough to greatly diminish quality of life, and increase risk for a number of diseases associated with hypothyroidism.

Another way of looking at percentile analysis is “quartile” analysis – which quarter does it fall inside of? Obviously it would be ideal to be in the 2nd or third quartiles.

A Cautionary Note on TSH

TSH (thyroid stimulating hormone) is not a thyroid hormone. TSH is a hormone that comes from the pituitary gland. The pituitary gland is told to release TSH by the hypothalamus, a part of the brain that monitors nerve signals, and converts those signals to hormone signals. TSH does not provide any information about the level of thyroid hormones. It does not provide any information about how efficiently the body is able to convert T4 to T3.
The best way to understand TSH is that is actually may stand to “Too Slow to Help”, because by the time TSH becomes elevated, a patient has had thyroid disease for months. It is common to see “normal” TSH even when thyroid hormone tests, or thyroid anti-body tests, are abnormal.
The following charts contains a few of many samples in which TSH was “within normal range”, while other markers of thyroid health were abnormal. The numbers are using percentile analysis. Even though all of the TSH levels are “normal” – with most of them even below the 30th percentile, each of these cases had many symptoms of thyroid disease, and other lab tests showed evidence of thyroid disease.

Optimal Ranges

Percentile and quartile analysis is becoming increasing important as new research validates clinical observations that patients do much better when they are not “barely normal”. Optimal ranges make it very clear that there is a great difference between “normal range” and ideal range.
A March, 2012 study revealed that “even within the normal range, TSH in the upper limits might exert adverse effects on the lipid profile and thus might represent a risk factor for hypercholesterolemia and hypertriglyceridemia.” So, if TSH is “normal”, but close to the top of the reference range, the person is more likely to have problems with excessive cholesterol and triglycerides, which also increases the risk for diabetes. The higher the TSH (within normal range), the higher the  cholesterol and triglycerides. The ideal range for
TSH is the first quartile – 25% or lower in the reference range. [1]
A few years prior to that study, other researchers found that they could predict how much fat a person had based on their free T4 levels within normal range. People with free T4 in the fourth quartile had less subcutaneous fat. [2]
A 2011 study demonstrated that heart failure patients with T3 levels in the lowest third had a much poorer prognosis than patients who had T3 levels above the 33rd percentile. [3]
Clinicians that have experience with thyroid disorders typically notice that patients do much better when their thyroid hormone levels are above the 30th percentile, ideally at or a little above the 50th percentile.

Ratio Analysis

Perhaps one of the greatest analytical tools available to clinicians is the ability to determine best outcomes by analyzing the ratio between two or more lab tests.
In ration analysis you don’t just look at T3 levels, and then at T4 levels, you see how they relate to each other – mathematically. Research on the ratio between T3 & T4 as well as the ratio between Reverse t3 and T3 have provided valuable insights into a number of conditions.

Free T3 : Free T4 Ratio

 The FT3/FT4 ratio is an indication about how effectively the body is able to convert T4 to T3. A higher FT3/FT4 ratio means the body is able to make more T3 (triiodothyronine), the more potent thyroid hormone.

Patients with Metabolic syndrome patients had lower FT3/FT4 ratio. They also had higher fasting blood glucose, higher triglycerides, higher systolic and diastolic blood pressure and lower HDL-cholesterol. [4] A higher FT3/FT4 ratio is associated with decrease risk of death in patients with dilated cardiomyopathy [5], and increased ejection fraction in patients with congestive heart failure [6].

Free T3 : Reverse T3 Ratio

The FT3/RT3 ratio is an indication about how the body is able to make T3 (triiodothyronine), instead of the non-active RT3 (reverse triiodothyronine). A lower FT3/RT3 ratio means the body is making too much of the non-active RT3.
The FT3/RT3 ratio is lower in a number of clinical conditions, including; cardiac heart failure (CHF) patients with New York Heart Association (NYHA) class II-IV [7]; Tuberculosis patients [8]; stroke patients [9]; after surgery and surgical complications [10, 11]; as well as caloric restriction and fasting [12, 13].

Avoiding Inconclusive Tests

There is a word in diagnostic medicine that is used to describe test results that do not give valuable information. That phrase is “inconclusive”. For example, if a patient is told that their “thyroid tests came back normal” and the only tests that was done was TSH, then a more appropriate term would be that the test results are “inconclusive”. Inconclusive means that a good conclusion cannot be made based on the lab tests that were ordered. A good synonym for “inconclusive” is the word “worthless”. In any event, it is best to avoid tests that ultimately provide inconclusive results. TSH is interesting – more academic – as part of a thyroid panel. But the gold standard of thyroid hormone tests needs to be the actual testing of thyroid hormones.

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About the Author

about_us-josephjcollins--element62Dr. Joseph J. Collins, RN, ND – President of Your Hormones Inc.  His naturopathic practice has always focused on an integrative approach to healthcare, with an emphasis on endocrinology and cellular signaling, with an integrative and functional approach. His practice encompasses adrenal, thyroid and glycemic function, as well as women’s hormone health and men’s hormone health through support of optimal cellular signaling, which he supports with foods, nutrients, phytotherapies, essential fatty acids, co-enzymes, adjuvant therapies and systemic enzyme therapy. By training, he is both a Naturopathic Physician and a Registered Nurse and is licensed as a Naturopathic Physician by the state of Washington. He graduated in 1993 with a Doctor of Naturopathic Medicine degree from the National College of Naturopathic Medicine in Portland, and has been licensed as a Naturopathic Doctor (ND) since 1993. Check out his website at, follow him on Twitter and Facebook.

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[1] Wanjia X, Chenggang W, Aihong W, Xiaomei Y, Jiajun Z, Chunxiao Y, Jin X, Yinglong H, Ling G. A high normal TSH level is associated with an atherogenic lipid profile in euthyroid non-smokers with newly diagnosed asymptomatic coronary heart disease. Lipids Health Dis. 2012 Mar 27;11:44.
[2] Alevizaki M, Saltiki K, Voidonikola P, Mantzou E, Papamichael C, Stamatelopoulos K. Free thyroxine is an independent predictor of subcutaneous fat in euthyroid individuals. Eur J Endocrinol. 2009 Sep;161(3):459-65.
[3] Brenta G, Thierer J, Sutton M, Acosta A, Vainstein N, Brites F, Boero L, Gómez Rosso L, Anker S. Low plasma triiodothyronine levels in heart failure are associated with a reduced anabolic state and membrane damage. Eur J Endocrinol. 2011 Jun;164(6):937-42. Epub 2011 Mar 31.
[4] Tarcin O, Abanonu GB, Yazici D, Tarcin O. Association of metabolic syndrome parameters with TT3 and FT3/FT4 ratio in obese Turkish population. Metab Syndr Relat Disord. 2012 Apr;10(2):137-42.
[5] Kozdag G, Ural D, Vural A, Agacdiken A, Kahraman G, Sahin T, Ural E, Komsuoglu B. Relation between free triiodothyronine/free thyroxine ratio, echocardiographic parameters and mortality in dilated cardiomyopathy. Eur J Heart Fail. 2005 Jan;7(1):113-8.
[6] Kimura T, Kanda T, Kuwabara A, Shinohara H, Kobayashi I. Participation of the pituitary-thyroid axis in the cardiovascular system in elderly patients with congestive heart failure. J Med. 1997;28(1-2):75-80.
[7] Savastano S, Cannavale V, Valentino R, Tommaselli AP, Rossi R, Luciano A, Tauchmanovà L, Mariano A, Mazzitelli L, Macchia V, Lombardi G. AlphaANP, AVP, and pituitary-thyroid axis in patients with congestive heart failure and acute respiratory failure. J Endocrinol Invest. 1999 Nov;22(10):766-71.
[8] Yan SM. Clinical study on thyroid hormone levels in tuberculous patients. Zhonghua Jie He He Hu Xi Za Zhi. 1991 Oct;14(5):298-300, 320.
[9] Hu R. Changes in serum thyroid hormones in acute cerebrovascular apoplexy and their clinical significance. Zhonghua Shen Jing Jing Shen Ke Za Zhi. 1990 Apr;23(2):87-9, 126.
[10] Goode AW, Herring AN, Orr JS, Ratcliffe WA, Dudley HA. The effect of surgery with carbohydrate infusion on circulating triiodothyronine and reverse triiodothyronine. Ann R Coll Surg Engl. 1981 May;63(3):168-72.
[11] Calvey HD, Marshall WJ, Marsden PD, Davis M. A new prognostic index in surgery and parenteral feeding: the ratio of triiodothyronine to reverse triiodothyronine in serum (T3/rT3 ratio). Clin Nutr. 1986 Aug;5(3):145-9.
[12] Moinade S, Glanddier Y, Lambert M. Thyroid hormones during a hypocaloric diet in obese patients. Pathol Biol (Paris). 1985 Jan;33(1):27-33.
[13] Garrel DR, Todd KS, Pugeat MM, Calloway DH. Hormonal changes in normal men under marginally negative energy balance. Am J Clin Nutr. 1984 Jun;39(6):930-6.

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