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Why Your Thyroid May be Under-Functioning Even Though Your Blood Work is Normal

Dr. Annie Cannon, ND blog-image1

You’re tired all the time, can’t lose weight, feel cold, have constipation, joint and muscle pain, and tend toward depression…
…but your blood work came back “normal”.

In my previous post, “Why You Don’t Have The Energy to Work Out,” I alluded to functional hypothyroidism as a culprit. Here, I am going into more detail about this condition.


The thyroid hormones control the metabolism of every cell in the body. More hormone increases metabolism (more energy and heat production, faster bowel transit time, etc.), and less slows metabolism down.

Let’s first review the definition of reference ranges…

Reference ranges are established based on what is typical for a group of healthy people of a certain age, sex, or other characteristic. Each lab has it’s own reference range. They are statistical numbers and not based on optimal values (except for vitamin D, which now has multiple reference ranges indicating optimal levels- yay!). Lab results always need to be taken into account with the patient’s symptoms and signs to make a diagnosis.


Each person will respond differently to a particular amount of thyroid hormone, but many doctors are seeing hypothyroid-like symptoms in patients with thyroid hormone levels that are “within range” which has led them to use alternative, usually narrower, reference ranges, based on how their patients feel. Just because you aren’t pathologically sick, does not mean you are optimally healthy.

In the conventional medical system, thyroid-stimulating hormone (TSH) is tested first to screen for thyroid problems. This is the hormone that comes from the brain and tells the thyroid gland to make thyroid hormones (T4 and T3). If this is within range, no further tests are done. If TSH is out of range, the thyroid hormones T4 and T3 are tested. However, in my experience, TSH is rarely out of range, meaning patients don’t usually get to have their T4 and T3 tested.

TSH is a valuable screening tool but it does not show the whole picture.

T4 converts to T3, the active thyroid hormone. If you are deficient in the various nutrients and co-factors needed for this conversion to take place, your T3 will be sub-optimal (not necessarily low by reference range standards), and your TSH will be normal because it sees that there is lots of (inactive) T4 around. This is also why many people on Synthroid (T4 only) still have hypothyroid symptoms.

Our tissues can also become resistant to thyroid hormone, even if there is enough around, which may or may not show up on blood work.


The following nutrients and co-factors are needed to support thyroid hormone production, conversion, and tissue sensitivity:

  • Iodine: the popular switch to sea salt means less use of iodized table salt, and the presence of the thyroid-disruptor bromine in sodas, pesticides, baked goods, pools, plastics, and flame-retardants displaces iodine, the central molecule in T3 and T4.
  • Zinc
  • Iron
  • B vitamins
  • Vitamin A
  • Vitamin C
  • Selenium
  • Tyrosine
  • There are also certain herbs that have been found to improve thyroid function, such as ashwagandha.

Stress down regulates thyroid hormone production and conversion directly, as well as impairing the adrenal glands’ output of cortisol. Cortisol must be balanced to allow optimal production and conversion of thyroid hormones. Treating the adrenal glands is often a first step to regaining thyroid function.
We also need to have optimal gut and liver function since much of the hormone conversion occurs in these areas!

If you have hypothyroid-like symptoms, see your naturopathic doctor to review your thyroid labs, to determine if a full thyroid panel would be beneficial, and for a thyroid-boosting treatment protocol.

–Dr. Annie

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