Are you Using Circadian Rhythms to take your Thyroid Replacement Hormone?



Thyroid Hormones, whether created in the body, or manufactured and found in a bottle, are all about getting 'ENERGY' to where it is needed in each and every individual cell of your body!


The Thyroid Pathways can be complicated and the correct production and conversion of thyroid hormones is affected by many things and many interactions with other endocrine and major organs and their associated hormones.

It is true that often when we find out that we have a thyroid problem, that the measuring of our hormones becomes one of the key things we focus our attention on. However, we often do not think about the variation of levels that those hormones go through each day, or why they are ever changing in response to the different tasks or situations we find ourselves in each day!





For example, if we are doing a lot of energetic and strenuous physical work, our energy demands on the cellular level of our muscles and our bones etc. would be different to a relaxed and lazy day.

Equally, if we are in stress, at a situation or the threat or thought of an upcoming worrying situation, our body will be using a lot of energy through the hormonal pathways, as we convert high levels of adrenaline or cortisone and our body gets ready for the situation or conflict that we are imagining and expecting to happen!

Different types of energy are required for these different body functions - but it is still ENERGY!!

The THYROID is JUST ABOUT PRODUCING ENERGY. It does not get concerned about how it is being used.

So if our thyroid is producing hormones to provide us with usable energy every day - it may just be worth looking at how the day may affect our hormone levels, right?

You might be surprised to know that an under-considered aspect of thyroid hormones is that the levels change during the day.

Yes! Your Thyroid Hormones, especially fT3 and TSH are regulated via Circadian Rhythms!!

Circadian Rhythms

What are these?

The term circadian comes from the route 'circa' (latin meaning "around"); 'diem' (latin meaning 'day).

"A circadian rhythm is a roughly 24 hour cycle in the physiological processes of living beings, including plants, animals, fungi and cyanobacteria. In a strict sense, circadian rhythms are endogenously generated, although they can be modulated by external cues such as sunlight and temperature."

These 'rhythms' are what we are referring to as the repeated 'completed' cycles that we see in nature that underpin how and when we act in the World. They create patterns of behaviours that define when we need to eat, to sleep, to hunt, to rest etc.

We are also always responding to other rhythms - including ultadian rhythms (being shorter than a 24 hour period: such as a sleep cycle) and infradian rhythms (being longer than a 24 hour period: such as menstrual cycles or seasons).




Times & Seasons for all things

So it seems reasonable, when we think about it, that our energy requirements and levels would change throughout the natural 24 hour cycle.

For many of us (who do not work shifts, or night work), the above image helps us to identify that many different body systems are operating differently at different times of the day - depending upon what is the usual 'pattern' of activity for a normal day.

In the image below, we can see that a lot of our hormonal activities are occurring at night.

They include: TSH (Thyroid Stimulating Hormone) levels increase, Leptin levels increase, HGH (human Growth Hormone) levels increase &

Melatonin, which is the hormone responsible for helping us to sleep.

It is well known that many of our rest and repair functions are happening during sleep time - and it would seem reasonable therefore for us to consider that the increase of the hormones used during sleep time might be related in some way to those rest and repair functions.



Thyroid Hormones & the 24 hour clock

TSH is at its peak levels between 02:00 and 04:00hrs and at its nadir (lowest) levels between 16:00 and 20:00hrs.

Studies have shown that there is a correlation between our TSH levels and our fT3 levels.

There is an increase in fT3 levels that occurs approximately 90 minutes after the increase in TSH levels!

However, there is little evidence of fT4 levels changing. This can be due to the longer half-life of fT4 (of7.6 days) as compared to fT3 (of 3/4 of a day) - meaning that fT4 does not fit into a circadian cycle and therefore making it not measurable as a circadian rhythm).


It can be helpful to understand the peaks and troughs of our thyroid hormone levels over the 24 hour period for