Why I Needed to Create the Circadian T3 Method (CT3M) and Why it Can Be So Helpful in Thyroid Patient Treatment

CT3M stands for Circadian T3 Method.

I created this approach over twenty years ago, in order to raise my cortisol from a desperately low level to a healthy level.

It requires no use of hydrocortisone or adrenal glandulars to do this. It just the use of T3 thyroid medication (Liothyronine). For some people, it can also work with natural desiccated thyroid (NDT).

Let me explain how I came to create (or discover) the Circadian T3 Method (CT3M).

I had been on T3-Only (with no T4 medication at all), for about 6 or 9 months and felt better in many ways. However, my low cortisol issue was still there.

Low cortisol showed up in my 8:00 am morning blood test. On a 24-hour urinary cortisol collection, my total and free daily cortisol levels were near the bottom of the reference range. I had low cortisol all day long.

However, I had passed a Synacthen test (ACTH Stimulation test), so my adrenals themselves were healthy. This latter situation is quite common with many thyroid patients, and I will return to this point.

In terms of low cortisol symptoms, my main ones were fatigue, low blood pressure, passing out (fainting) and weight loss. I was so weak that I was virtually housebound, and had to spend a lot of my time laying down. The passing out instances became quite frequent and were linked to low blood pressure.

For part of this time, I was struggling at work. Several times, I woke up in a corridor being looked at by worried colleagues.

My weight loss was severe. I had gone down from 170 pounds (12 stones or 76 kg) to 110 pounds (just under 8 stones or 50 kg), i.e. I had lost about 35% of my body weight. In contrast to most cases of poorly treated hypothyroidism, which causes weight gain, severe low cortisol can cause severe weight loss. I looked extremely ill.

I had been reading endocrinology books for a while and was aware of the pattern of FT3 over 24 hours, and the pattern of cortisol over 24 hours. Here are two charts showing these. You can click on this link and then use you’re ‘go back’ arrow on your browser to come back to this blog post. These charts are straight out of medical literature, and this is the knowledge that has been around for a very long time: Thyroid Hormone and Cortisol Charts

TSH is known to have larger and more frequent pulses in the night and can be seen to peak around 3:00 am in the morning. TSH is at its lowest in the afternoon.

FT3 is interesting too. FT3 peaks an hour or two after TSH peaks. It is also at its lowest in the middle of the day.

FT3 peaks in the night following the high point of TSH for two reasons:

TSH drives a healthy thyroid gland to produce more T3 and more T4.

We also know there is a connection between the TSH level and the rate of conversion of T4 to T3. When TSH is higher, the conversion rate of FT4 to FT3 increases. When TSH is lower, the conversion rate is lower. So, a high TSH in the night not only requests more T4 and T3 production from the thyroid gland, but it also increases the conversion rate of FT4 to FT3. Hence, FT3 increases in the middle of the night. In actual fact, TSH affects the regulation of the number of deiodinase enzymes being produced – which is why it affects the conversion rate of T4 to T3.

It should be immediately obvious that there is not a huge variation in FT4 – it reduces slightly when there is more conversion to FT3, and it increases slightly when the conversion rate to FT3 reduces.

So, I knew all of this information already at this stage of my attempt to recover from hypothyroidism.

Looking at the cortisol rhythm, it is easy to see that cortisol begins rising around 3:00 am and climbs to a peak between 7:00 am and 9:00 am in most people. This is to get us primed-up and ready to start the day. After this, cortisol normally declines steadily during the day, until the cycle repeats itself.

I knew my cortisol was very low and I was searching for an answer. 

I was on T3-Only medication. At that time, I took 3 daily doses. One when I awoke in the morning, one around lunchtime and one in the late afternoon/early evening. 

It occurred to me that, just like other thyroid patients, I was taking daytime thyroid medication. This tends to suppress the TSH, and the action of the thyroid gland (if someone still had a functioning thyroid gland at all).

The second thing that taking daytime thyroid medications tends to do is to achieve good levels of thyroid hormone (FT3) in the daytime, but this FT3 is going to be lower during the night because we do not keep receiving the medication during the night. The use of daytime thyroid medication isn’t a physiological replacement pattern at all. People on thyroid medication tend to have a lower TSH than healthy people have. Plus the normal, healthy pattern of FT3 is far less likely to occur.

I had worked this much out but still had not understood why my cortisol was so desperately low. I was confused! 

Then, one night, I just woke up around 3:00 am and I had the answer. I had seen the connection – part of the answer lay in the two charts and their relationship.

We know from research that the pituitary gland has the highest concentration of FT3 in the body – more than any other organ or body tissue. The pituitary makes its own D2 deiodinase enzyme and uses it to convert the FT4 flowing through it to extra FT3. Much of this FT3 remains within the pituitary in order to keep its own T3 levels high. The pituitary gland runs on T3 – as a car runs on fuel!  

The answer I had been searching for lay deep within the pituitary gland. If the pituitary was not receiving (or being able to create) the level of FT3 that it used to have, how could it function normally?

A person with lower FT3 levels than they had when they were healthy could easily have pituitary dysfunction. In this case, one of the pituitary hormones, like ACTH, could be lower than it used to be when the person was healthy. ACTH is the signal that drives the adrenal glands to make cortisol and Dhea. The adrenals usually perform well if they have enough cholesterol and an adequate ACTH signal. But without enough FT3 – all bets are off!

By the time I got up the following morning, I had the entire hypothesis worked out. I had low FT3 in the nighttime! This could be causing poor pituitary function and lower than adequate ACTH, thus low cortisol. I just had to test this hypothesis. 

The following night I set my alarm to take my first T3 dose about 2 hours prior to my normal get out of bedtime. I took it that coming night and I did feel a LOT better during the day. So, the next night I took it 3 hours before the time I usually got up. I felt better again! I was on to something here. This finally made sense.

I waited a couple of weeks to ensure that the improvement held – it did. I was elated. I went to see my family doctor. I explained it all – in fact, I bombarded her with science and evidence. I then asked her if she would support me by allowing me to do multiple 24-hour urinary cortisol collections. She agreed! So, this started a 6-month long experiment.

I went back to daytime only dosing for a week and then did a 24-hour urinary cortisol collection. I then moved the first dose to 30 minutes before getting up and waited a week and then did another cortisol collection.

I repeated this process about 8 times. The last 2-3 tests were done by moving the first dose a full hour earlier.  It was amazing that my doctor supported me. However, I had been sick for so long and medically retired by my company at this stage and I was still extremely ill – so I think she was desperate for an answer too.

The results were incredible!

Every time I moved the first dose earlier by 30 minutes, both total and free cortisol levels rose. I tested it to about 6 hours before getting up – to mirror the rise in natural FT3 rhythm. Once I got to about 4-5 hours prior to getting up there was no further benefit in taking it earlier, and it actually started to reduce the cortisol level beyond that.  However, the correlation between the time the T3 was taken and both free and total cortisol levels was virtually linear. The earlier the dose, the more cortisol. It supported my hypothesis totally.

I began referring to the approach as the Circadian T3 Method or just CT3M.

I stuck with about 4 hours before getting up time for my CT3M dose. I got an immediate benefit from CT3M and it enabled me to begin to function quite well again. I even began to exercise and started on the long road to recover my fitness. Over the following few years, my cortisol slowly improved. I have been using CT3M for many years now. If I try to not use it, my cortisol levels lower and I feel unwell. 

I have also discovered, in the past year, that I have both copies of the DIO1 and DIO2 gene defects. DIO2 can impact the production of effective D2 enzymes. Thus, this could also have impacted my pituitary and its abilty to convert FT4 to FT3, when on T4 and NDT medication.  By the time I was on T3-Only during the daytime, it was the strictly daytime use of T3-Only that was the issue.

I published Recovering with T3 in 2011. The majority of this book is about the safe and effective use of T3-Only and the protocol for doing that. Only a small part of it introduced CT3M and its potential benefits to those with low cortisol. It included a protocol for starting CT3M, and determining the correct CT3M dose size and timing. 

In 2013, I published The CT3M Handbook, with more information on using CT3M. I have worked with thousands of thyroid patients now and many of them have also improved their cortisol levels using CT3M. Some have regained their lives in dramatic ways through using it. It can work with NDT in some cases, but T3 works best. However, a T3 CT3M dose and daytime NDT is something that thyroid patients opt for quite often. 

In 2018, I published The Thyroid Patient’s Manual, which also explains how so many thyroid patients appear to have low cortisol. It also refers to CT3M but not in as much detail as the other two books,

These books now form a series, which deals with recovering from hypothyroidism: The Recovering from Hypothyroidism series.

I recommend reading them in this order: The Thyroid Patient’s Manual first, Recovering with T3 second and The CT3M Handbook for those that need even more information on CT3M.

I no longer believe in the concept of Adrenal Fatigue. I do not believe that the adrenals get tired at all. If they could get tired, those with Cushing’s disease would not be able to have super-high cortisol levels for years. I actually believe that most cases of low cortisol are caused by hypothalamic-pituitary dysfunction and the lower than normal ACTH signal that goes with this.

Sometimes, there is no known cause for hypothalamic-pituitary dysfunction, but yes, stress could well be a factor. In some cases, the low cortisol is due to the way we use thyroid meds and the fact that this is not physiological. In these cases, CT3M can bring about profound improvements in cortisol levels throughout the day. Results with many thyroid patients have shown how worthwhile a trial of CT3M can be. 

It is a shame that so many thyroid patients who are taking T4, NDT or T3 medication are sometimes persuaded to use hydrocortisone or adrenal glandulars to ‘top-up’ their cortisol levels. This often does not work well, as the added cortisol in these medications simply causes the pituitary gland to produce even less ACTH, and the patient’s own adrenals produce less cortisol. This frequently leads to the dependence on a full replacement dose of cortisol and the issues associated with this (needing to carry stress doses, needing to carry some kind of medical bracelet or medallion in case of emergency hospitalisation etc.).

CT3M is often worth a trial first before going down these routes. In many cases, CT3M raises cortisol right across the day. In some cases, it does not work as well or at all, depending on the severity/nature of the hypothalamic-pituitary axis issue. In a few cases, the issue is actual adrenal damage – but this is far rarer. 

Note: CT3M can help low cortisol throughout the day and can even help dysfunctional patterns of cortisol with some highs and lows in the pattern. It certainly has helped many thyroid patients with low cortisol levels from the morning to the evening.

So, this is a little more background on CT3M. It explains how I came to discover it and why it can be so amazingly helpful.

I believe that the connection between T3 thyroid hormone and cortisol ought to be part of mainstream endocrinology.  I also think that CT3M ought to be in the ‘toolbox’ of every endocrinologist or doctor who is dealing with thyroid and cortisol issues. 

See also (an old video I made which describes CT3M):



I hope that you found this interesting.

Best wishes,


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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  1. Maarit on 9th June 2020 at 9:14 am

    Thanks for this blogpost! Do you know anything about cortisolreceptor-problems? My daughter (21) has problems with fatigue. She takes T4 and T3 and had some problems with her pituitary because of anorexia. Now her Cortisol-levels seem alright again, but she doesn’t feel any better and is gaining weight.

    • Paul Robinson on 9th June 2020 at 10:54 am

      Hi Maarit,

      Only that this can happen.

      There are many more things that could be going on though. Anorexia leaves people nutrient deficient and it is often hard to get some key vitamins and minerals to the right level. I would do the testing I recommend in my book The Thyroid Patient’s Manual and check the recommended healthy levels I list there. Often the lab ranges are just too wide and simply being in those ranges is not sufficient.

      Take care.

  2. Francislene on 30th September 2020 at 1:51 am

    Hi Paul,
    I m Brazilian and would love to test this method, but here in Brazil there are no drugs that contain t3 (only handled). How do I know the dose I need. I have a lot of arrhythmia with the use of t4 only. I have chased doctors, but the only thing they tell me is that everything is fine.

    • Paul Robinson on 30th September 2020 at 10:21 am

      Francislene, if you don’t have access to Liothyronine (T3) there then this would be very difficult to do. My book Recovering with T3 explains how to manage the T3 dosing safely and effectively. Every individual needs to have a dosage that works for them and this has to be slowly and carefully discovered. My book explains how.
      Best wishes, Paul

  3. Jaron on 24th January 2021 at 12:33 am

    Hi Is your CT3M suitable for ppl who had the Radioactive Iodine Therapy? I started taking Synthroid after RAI but symptoms appear as I get older. Then I switched to NDT but it didn’t help either. I ran into your blog and it’s eye opening. I want to try T4 amd T3 combination therapy. Please give me your thoughts and advices. Thanks!

    • Paul Robinson on 24th January 2021 at 11:13 am

      Absolutely, I know many thyroidless thyroid patients who have used my T3 protocol and CT3M successfully. In fact, lack of a thyroid gland makes the person far more likely to be too low in FT3 and have cortisol issues as a result.
      The Recovering with T3 book and The Thyroid Patient’s Manual book both have useful information on all this area.
      Best wishes, Paul

  4. Christel Hemeryckx on 11th April 2021 at 2:35 pm

    Hello, Is the CT3M suitable for people who fail the ACTH (Synacthen) test? Thanks in advance for your reply.

    • Paul Robinson on 11th April 2021 at 4:11 pm

      If the Synacthen test is a very bad fail with very little response to the ACTH injection then I’d say no.

      If the test is only a borderline fail it might well be worth trying CT3M as low night time T3 can contribute to poor adrenal response.

      I do know of some Addison’s patients who failed the test, and who take hydrocortisone, that tell me the CT3M helps to keep their need for HC lower than without CT3M.

      So, I guess you can tell from my response that there can be a grey area and depending on how bad the symptoms are and how low the cortisol is CT3M might or might not be worth trying.

      Hope this helps.

      Best wishes, Paul

  5. G on 11th July 2021 at 11:36 pm

    Hi Paul!

    Thank you for sharing with the world at large your experiences, methods and thoughts!

    I started out with adrenal glandular and after a month or so, it didn’t work for me.
    I am now trying out T3 (maybe T3/T4 if needed) and seeing how it goes.

    I have insomnia.
    Each day can be different:
    some days I manage to sleep less, earlier, more etc.

    I’m wondering how to approach this, in terms of timing:
    Should I be aiming for the time I would like to eventually wake up?
    or the time I wake up now (which is constantly changing)

    I took a small dose of T4/T3 as a trial and it made me sleepy quite early at night.

    [ I have had the reverse schedule for decades, since I was a teen:
    feeling all day like a truck run me over, and ‘waking up’ in the evening/night time, ready to roll.
    My temperature follows a similar pattern,
    thought not terribly low it just wouldn’t go up to 37C at all prior to thyroid supplementation,
    and the days it did, it was more towards evening, when it should have been coming down.

    My cortisol blood test result is unreliable, as I learned from what you wrote,
    since I test at 8:00, having gone to bed only a few hours before.
    Labs where I live close at 10:00 am, so I don’t really get a chance to test later.
    because the result is within range, doctors are not approving further testing…
    [it’s on the lower part of the range]

    Thank you!

    • Paul Robinson on 12th July 2021 at 10:52 am

      Hi G,

      This type of detailed question is better done via the Contact US section on the homepage to be honest.

      But I would pick a time between 2:00am and 6:00am as a start point and not vary it with when you actually get up. The adjust the dose size or timing based on symptoms and signs from that point onwards.

      There are quite a few blog posts on CT3M which can be easily found by searching for ‘CT3M’, e.g.

      Best wishes, Paul

      • G on 14th July 2021 at 5:23 pm

        Will do!

        Thank you –

  6. Sandra on 14th July 2021 at 8:55 pm

    I have both of your books. I’m having a hard time digesting them because my brain is so foggy. I just wanted to ask a quick question. I had my ACTH tested a month ago and it was within range. I recently started Ct3m and had my ACTH tested and it was off the charts high. Is there anyway my pituitary just got a little too excited with the morning t3 dose and got carried away?

    • Paul Robinson on 15th July 2021 at 9:18 am

      Hi Sandra, I assume before starting CT3M that you tested cortisol and found it to be low?
      Cortisol itself is usually the measure that is used to decide if CT3M is needed. ACTH is not the best measure.
      But anyway, yes, some people do respond well to a CT3M dose. If they do then making the CT3M dose much smaller or taking it nearer get up time can help a lot.
      However, you need to be looking at cortisol and symptom changes – not ACTH.
      Best wishes, Paul

  7. Sandra on 15th July 2021 at 7:34 pm

    Yes, it was suspicious low but not low low but all of the symptoms pointed to it being low. Shortly after starting the CT3M i was able to move the morning HC dose later and would at times forget to take my HC through out the day. About 3 days maybe, after starting CT3M, I took the am cortisol blood test and ACTH and they were both high,or above range. I don’t think cortisol would have tested high had I not taken some progesterone cream but I do believe it would have been much higher from CT3M alone. I can tell from symptoms,even without progesterone cream, and don’t feel very low in the mornings now.

    • Paul Robinson on 16th July 2021 at 7:36 am

      Sounds good Sandra. Hopefully, you will continue to feel better.

      You have to be careful with progesterone cream though as some labs that use cortisol testing get confused between progesterone creams / gels and cortisol, as the molecular formulas are so similar.

      Best wishes, Paul

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