Why The Circadian T3 Method is So Important to Thyroid Patients – Text Version

When a thyroid patient has symptoms, or test results, of low cortisol, The Circadian T3 Method (CT3M) can be enormously helpful in improving the cortisol levels. CT3M can help the well being of the thyroid patient. It should be a standard tool used in the treatment of thyroid problems and low cortisol by doctors and endocrinologists.

The measurement of cortisol is ideally done via a 24-hour adrenal saliva test, as this test is more insightful because it measures free cortisol samples over the day. I also favour combining this test with a more standard 8:00 am morning cortisol blood test.

The CT3M Handbook makes it very clear why CT3M is necessary for so many thyroid patients. It also makes it clear why low cortisol seems to be so common among thyroid patients.

CT3M attempts to mimic healthy hormone levels.

Let us look at thyroid and cortisol hormone levels over 24 hours in a healthy person. Please click on this link to view the graphs. You can go back on your browser to come back to this blog post. Here are the graphs:


The first set of graphs shows how TSH, FT4 and FT3 vary over 24 hours. It is obvious that in a healthy person TSH peaks after they go to sleep.

A peak in FT3 follows this peak of TSH. The peak in FT3 is likely to be due to a combination of increased thyroid output of T3 and increased conversion of FT4 into FT3. There is research that shows that elevations in thyrotropin (TSH) cause increased levels of FT4 to FT3 conversion. See my blog post on this: https://paulrobinsonthyroid.com/effect-of-tsh-on-conversion-of-t4-to-t3/

For a healthy person, a raised TSH at night would request that more T4 and T3 be produced by the thyroid gland. The fact that FT4 lowers and FT3 increases on these graphs may seem strange, but it is perfectly explainable due to:

  • The effect that TSH has on the conversion rate from FT4 to FT3 and
  • The increased thyroid output of T3. 

These two factors would account for both the peak in FT3 level but no increase in FT4 (in fact a slightly lower FT4 level), in a healthy person with a working thyroid gland.

Note: this explanation is not the one offered in the research article in which the graphs appear.

They explain the rise in FT3 due to the extra thyroid production of T3 during the night only. It really doesn’t matter too much which of these two views that you hold because the important fact is that FT3 rises in the night. I personally believe that the rise is at least in large part due to the increased conversion of FT4 to FT3. 

This elevation in night time FT3 is natural and it is what our bodies would have done prior to thyroid disease and being on thyroid medication.

The second graph shows the natural cycle of cortisol in the body. It is very clear from the graph that cortisol rises during the early hours of the morning and peaks around the time that someone gets up for the day.

This period of intense cortisol production I have termed the ‘main cortisol production window’ in the Recovering with T3 and The CT3M Handbook books. It occurs approximately four hours before someone gets up for the day.

My belief is that when the pituitary gland is driving the adrenals to produce high levels of cortisol, it requires excellent levels of FT3 in order to do this. The relationship between peaking FT3 levels and the ability of the adrenal glands to produce peak cortisol levels is clear to me. Having seen the results of CT3M in myself, and in thousands of other thyroid patients, I know this to be true.

Now, what happens with normal thyroid medication and the way in which its use is advised?

Well, in the cases of thyroxine, natural desiccated thyroid, or T3, the usual advice is to take this in the daytime. That is the advice almost all doctors give and have given since these medications were available.

What is the consequence of taking natural desiccated thyroid (NDT) or T3 medications only in the daytime?

The major consequence is that FT3 levels will peak in the daytime, and when someone goes to bed their FT3 levels will fall. As the night goes on the individuals FT3 levels will fall to be around the lowest of the twenty-four hour period by the time the pituitary and the adrenals are expected to work.

This will be even more likely if a thyroid patient is on a high dose of NDT or T3, as this will have suppressed TSH making it more likely that no improvement in conversion of FT4 to FT3 can take place.

This unnatural inverted FT3 pattern follows from taking daytime thyroid medications. This unnatural pattern is likely to be even worse for patients with damaged thyroid glands, no thyroid glands or suppressed TSH levels. 

The use of daytime thyroid medications makes it more likely that a thyroid patient will be prone to having issues with low cortisol. 

However, not all thyroid patients will have cortisol issues.  I believe that some individuals have more margin in their metabolisms than others. They appear to have ‘stronger systems’.

However, there does appear to be a somewhat epidemic level of low cortisol amongst thyroid patients. I believe that this low cortisol ‘epidemic’ is largely due to the taking of thyroid medications in the daytime, resulting in low FT3 levels during the time when the pituitary and adrenal glands begin to work extremely hard to raise cortisol levels.

CT3M is a logical, practical method.

CT3M uses thyroid medications that contain T3 (T3 or NDT) in order to reproduce what our healthy bodies would have done before we had thyroid problems.

CT3M mimics the natural pattern of FT3. It stops FT3 from dropping to a low and unhealthy level, which can impact cortisol.

Please be aware that I do not for one minute believe that ALL thyroid patients with low cortisol have this due to low FT3 levels in the night. There are many other conditions that can result in low cortisol levels. However, CT3M is one tool that appears to be relevant to the treatment of low cortisol. It is often worth trying to see if this corrects the issue without resort to using adrenal steroids. I believe that enabling our bodies to work on their own is much better if it can be done.

CT3M should be a standard tool in the treatment of thyroid disease when there is evidence of low cortisol.

A Future Vision

I can imagine a time when advanced time-release drug technologies can allow us to take T3 medication before bedtime and have it released at a precise time that will support the pituitary and adrenal glands.

I can even imagine that we will have technology that can have our T3 medication and NDT medication in a container and that we can program a device precisely to release the right amount of thyroid hormone in a natural way over twenty-four hours. Eventually, we will all be able to have the 24-hour profile of FT3 that is ideal for us… as unique individuals. This may be a very long way off… but I am sure that it will happen! 

Best wishes,


(Updated in February 2019)


Paul Robinson

Paul Robinson is a British author and thyroid patient advocate. The focus of his books and work is on helping patients recover from hypothyroidism. Paul has accumulated a wealth of knowledge on thyroid and adrenal dysfunction and their treatment. His three books cover all of this.

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