Background to the Circadian T3 Method (CT3M) including Three AUDIO recordings

Note: there are links to each of a three 10 minute YouTube audio recordings that describe how I came to develop the Circadian T3 Method listed at the end of this blog.

What is a Circadian Rhythm?

Various hormones in the body have a circadian rhythm. This means that they are not secreted in a steady way throughout the day. Their secretion follows a set pattern that is repeated every twenty-four hours and is typically linked to our patterns of sleeping and waking, or daylight and night. Cortisol is secreted by the adrenal glands, with a steady rise in production during the last four hours of sleep, usually between the hours of 4:00 am and 8:00 am. It is the rising level of cortisol that helps us wake up in the morning, with the highest level of cortisol in the bloodstream at around 8:00 am. Cortisol levels then fall gradually during the day and are at their lowest between midnight and 4:00 am in the morning. This circadian pattern of cortisol production is a medical fact and is not speculative. The exact times may vary depending on when someone gets up on a morning. 

Cortisol Circadian Rhythm

Cortisol production is linked to our sleeping and waking cycle. This means that cortisol production increases during the last four hours of sleep, which for most people is between 4:00 am and 8:00 am, hence the timings discussed above. For other people, perhaps shift workers, or people with a different pattern of sleeping and waking, this rise in cortisol will occur during their last four hours of sleep, whatever that time period happens to be.

In order to make this discussion a little simpler, I will assume that I am talking about people who have a typical sleeping and waking cycle. Therefore, I will assume that the highest level of cortisol production will be between the hours of 4:00 am and 8:00 am. I will refer to this period of time, during which the adrenals produce the highest volume of cortisol, as the main cortisol production window.

My Own Health History and How I Came to Discover the Circadian T3 Method

During the first year or two of using T3, my health improved but was not ideal. I did not know exactly why this was. I tried various options with my T3 medication but could not discover quite why I did not feel completely healthy. Eventually, it dawned on me that some of my hormones had a circadian nature and I found out about the cycle of cortisol secretion. I also discovered from endocrinology books that TSH typically reaches its highest level around midnight or 1:00 am in the morning and subsequently T4 reaches its highest level in the early hours of the morning as a result of the peak level of TSH.  Consequently, I concluded (correctly as it turns out) that people with normal thyroid hormone production must have peak free T3 levels in their body in the middle of the night, some time after TSH had peaked. I even considered that people with normal thyroid hormone production might have a high level of free T3 when their adrenal glands begin to work at their hardest - during the last four hours of sleep. This was a really good guess as it turns out (more on this later).

I also suspected that people on T3 containing medication may have low free T3 during this main cortisol production window - simply because most people take their T3 or T3 containing medication (T4/T3 or natural thyroid) during the daytime and not in the middle of the night.

Paul's Experiment with Measuring Actual Cortisol Levels

I began to experiment with using doses of T3 early in the morning before I got up. When I found that I felt better with a T3 dose at 5:30 am, what was happening started to become clear to me. I believed that because my adrenal glands were trying to do most of their work during the main cortisol production window, they would be trying to work at their maximum rate during the time when my T3 levels in my body were at its lowest. My last dose of T3 on the previous day was around 5:00 pm, so by 4:00 am nearly eleven hours had passed with no further T3 medication.

I decided to ask my family doctor to support me with an experiment involving a series of twenty-four hour urinary cortisol tests and measuring 24 hour total free cortisol and 24 hours total cortisol output. Through this experiment, it soon became apparent that the size and timing of the first T3 dose had a very significant effect on cortisol production. Here are a couple of actual test results that illustrate this effect. Note - the exact same T3 dosage was used in both cases - only the timing of the same T3 dose was changed.

I found that with my first T3 dose of 20 micrograms taken at 3:30 am, the results showed that my total cortisol output was 349 nmol/sample (reference range 50-319 nmol/sample) and my free cortisol index was 74.0 nmol/l (reference range 20-100 nmol/l).

When I had moved my first dose of T3 to 8.45 am the results were startlingly different. Total cortisol output had dropped to 81.0 nmol/sample and free cortisol index had dropped to 27.0 nmol/l.

The only difference between the first and second test was the time that the first dose of T3 was taken, in relation to the main cortisol production window. The size of the dose remained exactly the same. Adjusting the timing of my first T3 dose, in relation to when the adrenal glands were trying to do their hardest work, caused my total cortisol output to rise just above the laboratory reference range in the first test and fall close to the bottom of the reference range in the second test.

These two tests show just how much the timing of the first T3 dose may affect cortisol levels and how by adjusting the size and the timing of the first dose of T3 in the morning I was able to make a very significant change to my body’s production of cortisol. The timing of this first dose of T3 affected my testosterone level in a similar way. Even a timing change to the first T3 divided dose of half an hour was capable of changing cortisol levels. I measured cortisol levels at various different times and discovered a close, linear relationship between the time of the first T3 dose and the actual cortisol level and how I felt.

How This Circadian T3 Method Changed My Health

I found that the size and timing of the first dose of T3 provided an excellent and unexpected degree of control over cortisol (and testosterone). By taking my first T3 divided dose between 4:00 am and 5:15 am I began to feel really healthy for the first time since my thyroid problems started. I managed to do this without any requirement for additional adrenal support.

Unfortunately, this process had taken nearly three years from the start of using T3, because I was unaware of this technique of adjusting my cortisol level. Note - I did try to take this T3 dose at bedtime but this not only affected my sleep but it also did not provide my adrenal glands with enough T3 when they actually needed it.

The Circadian T3 Method is a good description of this technique as it utilises the circadian natural action of the adrenal glands and requires thyroid medication which contains pure T3 (not slow release). However, because it is a rather long description many patients are now calling it the CT3M or T3CM - it doesn't matter which as it is pretty obvious what is being referred to.

​Note I began using the CT3M about 13 years ago and I have had good health since that time and I have needed no adrenal support in the form of hydrocortisone or adrenal glandulars as a result. Yes - I've been using the CT3M for well over a decade!!!! I just wish I'd realised how relevant it was going to be to other thyroid patients because I would have communicated the CT3M sooner.

Recent Research

A relatively new research study has found that in healthy people T3 levels have a circadian rhythm, related to the cycles of TSH and T4. This results in FT3 typically reaching a peak in the body around 4:00 am.

The research is by Russell, W., Harrison, R.F., Smith, N., Darzy, K., Shalet, S., Weetman, A.P., Ross, R.J. The research article 'Free triiodothyronine has a distinct circadian rhythm that is delayed but parallels thyrotropin levels.' is published in J Clin Endocrinol Metab. 93(6):2300-6. June 2008. A link to the abstract is:

Perhaps it is not so surprising that this novel method was as successful as it was because it was actually emulating nature.

It is also worth noting that only by ensuring that the adrenal glands work as closely to how they did in good health can the numerous adrenal hormones be produced at the appropriate levels. Cortisol is only one of the glucocorticoid hormones and these cannot all be replaced at the natural levels by any bottles of medication. Of course sometimes replacement is the only approach that is possible, e.g. in Addison's disease, hypopituitarism or when the low cortisol is very severe and will not adequately respond to any other approach.

How Might The Circadian T3 Method Work?

The Circadian T3 Method (CT3M) came into being as a result of my understanding the relationship between my T3 medication, my cortisol levels and how I felt. The results I achieved were dramatic. No T3 dosage size was different. Only the timing of my first T3 dose was different and it dramatically changed my cortisol levels as measured with a standard hospital cortisol test provided by the NHS in the UK.

How could varying the timing of this first T3 dose during the last four hours of sleep make such a difference in cortisol levels?

I knew my adrenals were not really damaged. I had previously passed an ACTH stimulation test (Synacthen test) quite clearly.

It was the timing of my first dose of T3 that was making the difference.  This circadian T3 dose was timed exactly to raise FT3 during the period of time when my adrenal glands would be working flat out to produce the highest volume of cortisol for the day.

I am convinced that the CT3M works for patients because it is addressing too low a level of FT3 in the adrenal tissues during the last four hours of sleep (main cortisol production window). However, it is possible that some patients may have a subtle change in their hypothalamic-pituitary-adrenal axis as a result of prolonged hypothyroidism, which the extra FT3 helps to compensate for. It is also possible that a few patients may have some minor degree of adrenal atrophy or damage that a Synacthen test cannot find and that again the extra FT3 helps to compensate for. There are probably multiple causes of cortisol insufficiency that is not caused by Addison's disease or hypopituitarism.

This circadian dose of T3 may be in the form of T3 only replacement or the T3 contained as part of a T4/T3 combo or natural thyroid. Slow release T3 does not work as effectively.

Incidentally, I have never claimed that the CT3M will 'heal adrenals'. What does 'heal adrenals' mean anyway - it is a really vague statement. I do know that the CT3M does correct cortisol insufficiency in many patients. Does this mean 'healing'? Some of these patients who have recovered their health using the CT3M do view it as healing because they no longer need to use hydrocortisone or they are experiencing far better adrenal performance. Some might think 'healing' means that at some point then the early dose of T3 containing medication may no longer be required at an early time. It is too early to say whether any patients will be able to stop using the CT3M - I know I cannot. I suspect only a few patients may be able to stop using the circadian T3 dose at some point.

However, for many patients CT3M does correct cortisol insufficiency and in a manner that has been seen to be more effective than the use of one or more adrenal medications.

For some patients the adjustment of the timing of the circadian T3 dose is akin to having a 'control dial' on the adrenal glands - cortisol and other aspects of adrenal performance can be turned up and down by the careful adjustment of this circadian T3 dose. It is amazing and wonderful to see this happen and to see the results, which can be spectacular.

Some Practical Considerations

The Circadian T3 Method is described in full in my book 'Recovering with T3'. There are many subtleties in applying it and I recommend reading 'Recovering with T3' to learn these to any doctor or patient considering the use of the CT3M.

I always use many measures to ensure the safe and effective use of the CT3M. The symptoms and signs I use are described fully in 'Recovering with T3'. However, I do use heart rate, blood pressure and body temperature and a range of symptoms.

Changes in thyroid hormones and the interaction of these with the adrenal glands can produce changes in heart rate, blood pressure and body temperature. This is why a doctor or endocrinologist pays attention to BP and heart rate as well as laboratory test results. The adrenal glands are intimately involved in blood pressure regulation. Excess thyroid hormone can easily push up body temperature and heart rate and blood pressure - you only need to hear horror stories of people rushed into hospital with thyrotoxicosis from over-active thyroid glands to understand that this is possible. To not paying attention to blood pressure, heart rate and body temperature as well as symptoms and some laboratory tests would be negligent.

So, my book 'Recovering with T3' is totally focused on safety and as such I have always monitored heart rate and blood pressure (using a home BP meter) as well as temperature and symptoms. This is just a process of due diligence and using the CT3M does requires close attention to these measures and recording of them in order to assess the effectiveness of the CT3M.

Paying attention to all of these variables is essential during the adjustment of all thyroid medication - it is the only safe thing to do. It should not be unique to the CT3M or the T3 Dosage Management process described in 'Recovering with T3'.


The Circadian T3 Method works well for me. It raises my own cortisol levels from a clear cortisol insufficiency situation to a level that I can feel well with. It required no change in the amount of T3 I used at all.

The CT3M also fits well with known medical facts about actual cortisol circadian rhythm and actual free T3 circadian rhythm. It is firmly rooted in known medical facts of how our hormones actually work. The CT3M is simply attempting to mimic the high free T3 levels that are likely to exist in the tissues of the adrenal glands during those few hours before we wake up when the adrenals are producing their highest volume of cortisol.

I don't claim to have done anything particularly clever in developing the CT3M. I was very ill and I eventually turned to endocrinology textbooks in desperation. I found the basic facts of circadian rhythms of various hormones quite easily in several well-known texts and quickly put two and two together. It was pretty obvious to me once I'd seen the basic medical science. If I hadn't had a supportive family doctor I would never have got the tests done that backed up the basic idea of the CT3M. So, I was just the right person, in the right place with their health at the right time to realise something that is really pretty obvious. I don't claim that it is a stroke of genius or anything remotely like that. It does however happen to work really well in most cases and the CT3M presents doctors and thyroid patients with another useful tool which may be applied when the adrenal glands are not performing well enough.

The Circadian T3 Method is now producing far better adrenal function in the growing body of thyroid patients who are using it. It does not work for all patients and I have never said that it does. However, it does appear to work for the majority and in a way that is helping many to feel truly well for the first time in years.

I have produced an audio recording which is available on YouTube in three 10-minute bite-sized parts, which you may also find interesting. Together these three short recordings explain how I came to develop the Circadian T3 Method and why I believe it should be in the toolkit of thyroid patients and doctors in the fight against hypothyroidism.

Here are the three  links:  

Part 1: h

Part 2:

Part 3:

My warmest regards,