Thyroid Math: What Those Numbers Mean (and What Your Doc Probably Forgot to Tell You About Hypothyroidism)


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You may have low thyroid function, also called HYPO-thyroidism, and not know it. But let’s face it… thyroid numbers are often counterintuitive and confusing. When you combine hypothyroidism with the common low-thyroid symptom of brain fog, maybe even a bit of depression, and you’ve got a perfect storm for feeling overwhelmed, and even worse, disempowered about what to do next. In this article, I will clear up the confusion about what the numbers mean when it comes to your thyroid.

Want a sampler of how confusing thyroid math can get?

– TSH goes up when thyroid function is low (TSH stands for Thyroid Stimulating Hormone).

– Your thyroid makes T1, T2, T3 and T4 but your mainstream doc will probably only check TSH, and maybe free T4.

– T3 is 4-fold more potent than T4, because T3 is the active form of thyroid hormone. Keep this in mind when changing doses (for instance, prescription T3 at a dose of 25 micrograms = T4 at a dose of 100 micrograms)

– Natural Dessicated Thyroid? 1 grain of Armour Thyroid is the same as 60 mg, which consists of T3 at 9 mcg together with 36 mcg of T4. Naturethroid? Oh, Jeez! ! One grain is 65 mg… and oh my gosh, you get the picture!

Here’s the math I most want you to know:

Thyroid Math - What Those Stats Mean (and What Your Doc Probably Forgot)1. In 2002, the American Association for Clinical Chemistry (AACC) lowered the normal range for TSH to 0.3-2.5. Most docs don’t know this and are still using the old, pre-2002 range! Laboratories too. AACC  reported that: “In the future, it is likely that the upper limit of the serum TSH euthyroid reference range will be reduced to 2.5 mIU/L because 95% of rigorously screened normal euthyroid volunteers have serum TSH values between 0.4 and 2.5 mIU/L.” They also stated that “a serum TSH result between 0.5 and 2.0 mIU/L is generally considered the therapeutic target for a standard L-T4 replacement dose for primary hypothyroidism.” (Quotes from Mary Shomon’s website – thank you, Mary, for your awesome advocacy!)

2. Many folks are thyroid resistant, defined by a high reverse T3 and low free T3. But the tricky part is getting the units lined up and interpreting the free T3: reverse T3 ratio properly. Here’s how you know – use this calculator right here.

3. Broadening the lab diagnostic criteria to thyroid levels above 3 would mean that  suggests that more than 13 million Americans are likely to be defined as hypothyroid. That’s a lot of people!

4. Keep your free T3 in the top half of the normal range, and TSH in the lower half of the normal range, and all is good. Bonus prixe if you keep your reverse T3 in the lower half of the normal range!

5. Women are 10 times more likely to have thyroid problems than men, which is part of the reason that thyroid often gets overlooked or dismissed!

6. If you have the triad of weight gain, fatigue and depression–think thyropause. It’s a common cause of these symptoms especially for women starting in their 40s.

I consider personal power to be defined in this way:

You are fully able to understand, create, express and communicate effectively your intentions: for your mind, body, thyroid, relationships, work, finances, and _______ (fill in the blank). You are powerful when you get what you intend.

Let’s start with feeling your power around the thyroid. I intend for you to feel:

– Ease around your weight
– Overflow of energy to meet your daily challenges
– Stable, supportive mood
– Content and serene
– Like your hair is staying where it belongs: on your head, in your eyebrows and not in your shower drain.

Are you feeling it?


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Sara Gottfried MD About Sara Gottfried MD

Sara Gottfried, MD is the New York Times bestselling author of the new book, Younger: A Breakthrough Program to Reset Your Genes, Reverse Aging, and Turn Back the Clock 10 Years. Her previous New York Times bestsellers are The Hormone Cure and The Hormone Reset Diet. After graduating from Harvard Medical School and MIT, Dr. Gottfried completed her residency at the University of California at San Francisco. She is a board-certified gynecologist who teaches natural hormone balancing in her novel online programs so that women can lose weight, detoxify, and slow down aging. Dr. Gottfried lives in Berkeley, CA with her husband and two daughters.