Does a normal thyroid test always mean a normal thyroid?

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Does a normal thyroid test always mean a normal thyroid?

The Thyroid: Conductor of the Hormonal Symphony

Does a normal thyroid test always mean a normal thyroid?

That’s the question Life Extension’s Michael A. Smith, M.D., posed to Pamela Wartian Smith, M.D., M.P.H, M.S., who is the Director of the Center for Personalized Medicine and the founder of The Fellowship in Anti-Aging, Regenerative, and Functional Medicine, in this episode of Live Foreverish.

Thyroid Health

Is your thyroid “normal?”

A 45-year-old woman with bowel issues and dry skin is feeling fatigued and run down. She visits her primary care physician who correctly orders tests of the patient’s thyroid function
, all of which come back normal. The patient is then prescribed an antidepressant.

Thyroid Levels

What’s wrong with this picture?

“There’s a difference between optimal function and levels, and normal function,” Pamela Wartian Smith, M.D., responded. “What we like people to have is optimal function so they feel great every day. And before someone is put on a medicine for depression, we always do full thyroid studies and we want to have optimal levels. Full thyroid studies would be a TSH, a T3, free T4, reverse T3, and thyroid antibodies. And by optimal function, I mean that the TSH, which is the thyroid stimulating hormone, should be somewhere between the lowest limit of normal and 2 µIU/mL. Normal at the lab may be up to 5.5 µIU/mL. But with anything above 2 µIU/mL, the patient will have symptoms of hypothyroidism (low thyroid function).”

Dr. Smith added that borderline thyroid function test results are often associated with low iodine levels, because iodine is necessary for thyroid function.1 “We do an iodine test first, which is a urine test, to make sure they have enough iodine,” she noted. “If they don’t, we give them iodine, then repeat the thyroid function studies later. If they have normal iodine, then we look at prescribing them both T3 and T4 in most cases.”

Low Thyroid Levels

Another scenario

Another scenario is the patient who has low thyroid function and is being treated with T3 and T4 thyroid hormones but doesn’t respond well.

Some individuals have normal thyroid hormone levels, yet transport of thyroid hormones into the cells may be poor.2 Poor thyroid transport is sometimes reflected in high blood levels of reverse T3, another form of thyroid hormone that is also normally taken up by cells. Problems with the cells’ power plants known as mitochondria may be responsible for these transport issues.3 Treating conditions associated with mitochondrial dysfunction could be helpful. High reverse T3 can also be caused by infection,4 and possibly by over-supplementation with T4. If the infection is treated, and/or the dose of T4 is lowered and T3 is added, reverse T3 will usually come down.

Thyroid Treatment

Is treatment with T4 alone an issue?

“It certainly is,” Smith replied, noting that the medical literature has revealed that most subjects who needed thyroid hormone were found to do better if they were given both T3 and T4 rather than T4 alone.5-8

Armour Thyroid, Nature-Throid and Westhroid are desiccated thyroid extracts that provide T3 and T4 in naturally occurring ratios that are somewhat variable,9 but these medications aren’t right for everyone. Thyroid hormones can be compounded to allow for individualized adjustments to the ratio of T4 to T3.10 This is quite different than the “one size fits all approach” still prevalent in conventional medicine.

Getting back to the 45-year-old woman for whom low thyroid hormones are suspected but, instead, receives a diagnosis of depression, Dr. Smith recommended that she visit an endocrinologist or a primary care physician who has an up-to-date approach to thyroid hormones.

When asked, in summary, what she would like people to know about thyroid disorders
, Dr. Smith unhesitatingly asserted that “Thyroid is the most important hormone because it regulates everything in the body.”

She added that estrogen, progesterone, testosterone, DHEA, cortisol, pregnenolone, melatonin, and insulin may additionally need to be assessed.

“It takes many things to make the thyroid work well,” Dr. Smith observed. “The thyroid is what I lovingly call ‘the conductor of the hormonal symphony.’”

Like what Dr. Smith has to say? Listen to the Live Foreverish podcast with Life Extension’s Dr. Michael Smith and his guest Pamela Wartian Smith, M.D., M.P.H, M.S., as they discuss the thyroid, by visiting

If you like what you hear, please take a moment to give Live Foreverish a 5-star rating on iTunes


  1. Zimmermann MB. Lancet Diabetes Endocrinol. 2015 Apr;3(4):286-95.
  2. Koulouri O et al. Best Pract Res Clin Endocrinol Metab. 2013 Dec; 27(6): 745–762.
  3. Holtorf K. J Restor Med. 2014 April 1;3(1):53-68.
  4. Kim RB et al. PLoS One. 2018 Aug 20;13(8):e0202422.
  5. Hennemann G et al. Thyroid. 2004 Apr;14(4):271-5.
  6. Bunevicius R et al. Endocrine. 2002 Jul;18(2):129-33.
  7. Solter D et al. Exp Clin Endocrinol Diabetes. 2012 Feb;120(2):121-3.
  8. Nygaard B et al. Eur J Endocrinol. 2009 Dec;161(6):895-902.
  9. Rees-Jones RW, Larsen PR. Metabolism. 1977 Nov;26(11):1213-8.
  10. Paoletti J. Int J Pharm Compd. 2008 Nov-Dec;12(6):488-97.

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