A conversion problem can cause weight gain and on going symptoms, with hypothyroidism, due to inefficient levels of thyroid hormones. A conversion problem of thyroid hormones is often not considered by doctors to be a possibility for patients who don’t respond well to T4-only medication, but it is much more common than they realise.
If you are on T4-only medication such as Levothyroxine, Synthroid etc. and still don’t feel fully well, then it is likely you could not be converting T4 to T3.
A healthy thyroid gland produces five hormones: T1, T2, T3, T4 and Calcitonin. These five hormones are needed for pretty much every process in your body, especially T3 and T4. Although we have more T4 than T3, T3 is the most active. T4 is said to be about 90% of what the thyroid gland produces, with around 9% being T3 and adequate levels of both is what’s needed to help us feel well and carry out all our usual bodily functions and processes. However, we now know that it is not just about how much T4 is available, it is also about whether it is actually usable at the cellular level or not.
The main purpose of thyroid hormones, produced by the thyroid gland, is to ensure the metabolism is running properly. You might think that the metabolism’s job is just to burn calories, but it is also to produce heat and fuel to keep us warm and give us energy. Now, if we don’t have enough thyroid hormone, we have a slow metabolism, so will have symptoms associated with a slow metabolism, such as cold intolerance (from the lack of heat made) and extreme tiredness and weight gain (from the lack of calories burned to make energy), among lots of other symptoms of hypothyroidism that we all know about already.
An inability to properly convert T4 to T3 is common among thyroid patients and can result in a fluctuating TSH or a TSH that is ‘in range’ and a low Free T3. Many patients have an in-range TSH, but when they actually check their Free T3 and Free T4, they show that the T4 is not converting to T3, with a low Free T3. This can be caused by an enzyme called iodothyronine deiodinase that is either deficient or not compatible for some people. The enzyme iodothyronine deiodinase is important in the activation and deactivation of thyroid hormones. T4 is converted into T3 by deiodinase activity. A problem with this can therefore cause conversion issues, where TSH can look ‘fine’, as well as Free T4, but with a low Free T3 and continued hypothyroid symptoms and development of other health conditions (such as mental health and heart/blood pressure problems).
Conversion problems and issues with thyroid medication properly working can be caused by adrenal fatigue, or other vitamin deficiencies such as iron or selenium. By addressing these, you may fix the conversion problem, but many other people simply have a problem converting and don’t know why. But it’s a big reason as to why T3 and NDT medication tend to work better for a lot of patients, instead of T4-only meds like Levo or Synthroid, because it gives them direct T3, so they don’t have to rely on their body to convert it.
It still baffles me that doctors expect those of us with an already rubbish thyroid gland, which already doesn’t function properly, to also convert T4 in to the right amount of T3. It just doesn’t make sense!
If you’ve tried raising your dosage of T4-only meds and feel even worse, then this is a key sign that you have a conversion problem, as you don’t need anymore T4. You need more T3.
If your doctor runs thyroid test after thyroid test and says you’re still ‘fine’, even though you feel rubbish, then it could indeed be a conversion problem. If they only test TSH and T4, then this would not show up a conversion problem. A low Free T3 would show insufficient amounts of T3 in the blood, and if on NDT or T3 medication, then a high Free T3 indicates pooling, caused by low iron or adrenal fatigue, meaning your body isn’t using the T3 you’re putting in. By fixing a low iron or adrenal problem, you should fix the pooling.
I’ve read in a few books like Dr Barry Durrant-Peatfield’s, about how the body can manage the converting of T4-only meds in to T3 for so long, before eventually losing the ability to, because of the stress this puts on the body. Essentially, the body is already under stress by being underactive, so why add anymore? Why try to rely on it converting hormones, when we can simply put them in, ready to be used? I support the use of natural desiccated thyroid and T3 medicine, especially when problems like this show how incompatible T4-only medication is for a lot of people, as it gives the direct T3 and skips having to hope that it’ll convert. Sure, these medication options need to be managed correctly, and having a doctor work with you is the safest way to use them, and what I’d recommend if possible.
So what does a conversion problem do?
Not being able to adequately convert T4 in to T3 leaves you hypothyroid and not properly medicated. Your hypothyroidism isn’t properly managed, meaning you still have a lot of symptoms, and patients’ mental health also commonly suffers.
An underactive thyroid often comes hand in hand with depression and according to Thyroid UK’s survey in 2015, over 50% of the hypothyroid patients who took part in the survey, also suffered from depression. More than half. Of those taking antidepressants, 47% saw no difference. Of course not, the underlying problem, being the poorly treated thyroid, or possibly adrenals, isn’t being fixed.
How are they linked?
Stop The Thyroid Madness’ book looks at this in more detail. It explains the big part that T3 plays in our mental health. I strongly suggest you get the book; it’s great.
They say that having low Free T3 is a likely cause for depression, mood swings, anxiety etc. when on t4-only medicine, and suggest that once this is treated with direct T3, it should ease. It was certainly true for me. When I switched from T4-only Levothyroxine to NDT, which contains direct T3, my anxiety, depression and over-emotional tendencies lifted quickly and haven’t returned since.
T3 has an important role in the health and optimal functioning of your brain, including: your cognitive function, ability to concentrate, mood, memory and attention span and emotions and ability to cope with life’s stresses. Christiane Northrup, MD explains this further on her website, “[T3] is actually a bona fide neurotransmitter that regulates the action of serotonin, norepinephrine, and GABA (gamma aminobutyric acid), an inhibitory neurotransmitter that is important for quelling anxiety.” She also states: “If you don’t have enough T3, or if its action is blocked, an entire cascade of neurotransmitter abnormalities may ensue and can lead to mood and energy changes, including depression.”
STTM’s book says that T3 interacts with brain receptors and makes the brain more sensitive to chemicals such as Serotonin and Norepinephrine, which affects your alertness, memory, mood and emotion.
So if your doctor failed to check your thyroid levels with the correct tests, i.e not just TSH, but also Free T3 and Free T4,when you complained about the above symptoms, you may have mental health issues caused by an inadequately treated thyroid problem in the form of low T3, from conversion problems.
If they did check them and say they’re adequately treated, make sure they fall in to these areas, as backed up by various sources: TSH 0.5-2, Free T3 top quarter of the range and Free T4 mid range or a bit higher.
You do need all three doing, as doing just one or two isn’t accurate.
I have a conversion problem, and when taking T4-only medicine Levothyroxine, even when I felt unwell still and raised the dosage a little, it made me feel worse, due to putting in too much T4, when what I needed was more T3. My body wasn’t converting it to T3. I changed to NDT, which contains T3, and have come on in leaps and bounds. I’m about 90% back to full health and now my TSH, Free T3 and Free T4 all read very, very well.
If you found this article informative, useful, helpful or in other words are grateful you stumbled across it, please consider helping me keep The Invisible Hypothyroidism running, so that we can carry on building a strong community, spreading awareness and helping each other. Running the site comes at the expense of my personal time and money from my own pocket. You can make a one-off or monthly donation to support me keeping this website going, by clicking the button below.
You can click on the hyperlinks in the above post to learn more and see references to information given, but more reading and references can also be found at:
To get notified of all my posts, blogs and articles, like my Facebook page here: https://www.facebook.com/TheInvisibleHypothyroidism/
And follow me on Instagram.
I run a Facebook group, called Thyroid Family: Hypothyroidism Advice & Support Group. This group is for underactive thyroid/hypothyroidism patients only, and not medical professionals or anyone else. If you have any questions on living with hypothyroidism, or want some support, help or advice, please join us.
I also run a group for the spouses, partners and other halves of hypothyroid patients, called Hypothyroid Patients Other Halves – Support & Advice Group. This is for the other halves only and not patients.