Liothyronine use in a 17 year observational population-based study - The tears study

Not long ago, diogenes posted this:

Apparently there are few longterm ill effects from taking T3 only or T3/T4 combination

Today I noticed a new paper from Dundee saying something similar:

Clin Endocrinol (Oxf). 2016 Mar 4. doi: 10.1111/cen.13052. [Epub ahead of print]

Liothyronine use in a 17 year observational population-based study - The tears study.

Leese GP1, Soto-Pedre E2, Donnelly LA2.

Author information

1Department of Endocrinology and Diabetes, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK.

2Division of Cardiovascular & Diabetes Medicine, School Of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK.



To look at adverse outcomes for patients on liothyronine compared to l-thyroxine. Some trials have examined the relative merits of liothyronine but none have looked at adverse outcomes in large numbers


An observational study of all patients prescribed thyroid hormone replacement in Tayside Scotland (population 400,000) from 1997 to 2014.


A study group of patients having ever used liothyronine (n=400) was compared to those who had only used l-thyroxine (n=33,955). All patients were followed up until end-point, death or leaving Tayside.


Mortality rates and admissions with cardiovascular disease, atrial fibrillation, fractures, breast cancer and mental diseases were compared. Incident use of bisphosphonates, statins, anti-depressants and anti-psychotics was compared.


Compared to patients only taking l-thyroxine, those using liothyronine had no increased risk of cardiovascular disease (hazard ratio (HR) 1.04; 95% CI 0.70-1.54), atrial fibrillation (HR 0.91: 0.47-1.75), or fractures (HR 0.79: 0.49-1.27) after adjusting for age. There was no difference in the number of prescriptions for bisphosphonates or statins. There was an increased risk of new prescriptions for anti-psychotic medication (HR 2.26: 1.64-3.11 p<0.0001) which was proportional to the number of liothyronine prescriptions. There was a non-significant trend towards an increase in breast cancer and new use of anti-depressant medications. During follow-up, median TSH was higher for patients on l-thyroxine alone (2.08 vs 1.07 mU/L; P<0.001).


For patients taking long-term liothyronine we did not identify any additional risk of atrial fibrillation, cardiovascular disease or fractures. There was an increased incident use of antipsychotic medication during follow up. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.


hypothyroid; liothyronine; safety; thyroid; thyroxine

PMID: 26940864 [PubMed - as supplied by publisher]

Have to say, how on earth did it come to pass that they had enough patients on T3 at all to do a study? Current situation seems to make the possibility of a follow-up or follow-on from this impossible in the UK. There won't be anyone prescribed T3. Unless they actually use patients who are self-medicating.

Added when I found it:

The TEARS study

20 Replies

I've been on liothyronine for almost 16 yrs now. I do suffer fast beating heart - tachycardia - but I had this prior to taking t3. I get mine via NHS due to allergy to thyroxine. Nice to know and thanks for the report. 'M'

Much obliged Helvella to your link. Thanks also, first of all to Diogenes and his team too who have come to the same/similar conclusion.

It just shows how 'out of date' the guidelines have been although the BTA recently addressed this issue by copying the ATA guidelines abut T3.

Helvella, interestingly the 20-year observational study in Diogene's link also found increased mental illness in T3-only patients but not patients on T4+T3 combination. Good to see neither study finds increased incidences of atrial fibrillation and osteoporosis/bone fractures.

I'd not place too much emphasis on that. The selection of the subset of patients who ever get any T3 is itself an issue to be investigated. Perhaps those who have suffered worst and longest on T4 monotherapy are the ones who have the most difficult to resolve mental issues?

The fact that the brain does a substantial part of its own conversion of T4 might be significant? Perhaps at least some T4 is desirable in most people in order to maintain the ability of the brain to convert its own on demand and largely independently of the serum T3 level?

Helvella, My mental illness preceded thyroid disease by decades. Hashimoto's was destabilising but I've not had Hashi's since thyroidectomy. There was substantial improvement in mood and cognition within days when I added T3 to T4 but no improvement in physical symptoms for 3 months. Since I've been stable on T4+T3 I've stopped anti-depressants.

Is it simply that the patients who were on liothyronine were being treated with it because of mental health issues not thyroid issues, therefore might be expected to have greater need for other psychiatric drugs? Like Rod, I think it's a marvel they found 400 patients - can't imagine they were all actually thyroid patients...

Or, and this seems more likely to me, given how scared doctors are of suppressed TSHs, simply that those patients on liothyronine only weren't actually on sufficient to resolve their symptoms, so they felt the need to give them supplementary psychiatric drugs.

I'd be happy to accept that anything is causing this result - but we (and everyone else) must avoid the simplistic assumption that taking liothyronine in and of itself is a cause. (In the fullness of time there might be something in that. But assumption is a devil.)

Jazzw, I don't think so. Looks like they were treated with T3 for thyroid issues and then prescribed anti-depressants.

"There was a non-significant trend towards an increase in breast cancer and new use of anti-depressant medications. During follow-up, median TSH was higher for patients on l-thyroxine alone (2.08 vs 1.07 mU/L; P<0.001). and "There was an increased incident use of antipsychotic medication during follow up."

There are over 3000 T3 takers on the Recovering with T3 site.

How many prescribed T3 and how many getting their own?

Also, in the context of Tayside, how many in the UK and how many not?

I can't answer that Rod. I am in UK and I am prescribed (at the moment!). Been on T3 for two and a half years. Using Paul Robinson's book to learn about titrating etc.

I wondered that about patient groups. Have heard that psychiatrists sometimes prescribe T3, so wonder if patients with pre-existing psychological conditions are more likely to get it.

I agree with helvella those 400 probably suffered for too long on T4 mono therapy. That certainly was the case for me. After self medicating for a year in NDT, a month ago I decided to go on T3 only. Early days yet, but the difference in my mood, concentration levels is noticeable and I'm glad so far.

After 10yrs on 50mcgs T4 and being continually told my thyroid was fine even though feeling ill I am quite relieved to have found an knowledgable endocrinologist who recognises when there is a need for added T3 which has been prescribed for me in a T4/T3 combo for 2 years now........but thankfully no mental health issues here.

I also sense winds of change here as hubby recently had a TSH test result of 6 confirmed by GP as above range and under medicated and instantly raised his Levo T4

He has also confirmed that our surgery will honour the need and prescribe T3 for patients when recommended by an endocrinologist.........

Now I call that a big step forward ......Wow!!

Perhaps in future there may be more than a small number of patients to survey if they are able to be given added T3 .

Don't know about over your side of the pond, but here some shrinks give T3 for depression. If that's the case over there, then it would explain the increase in anti-psychotic prescription meds as well. That alone make me suspicious about their study cohort. Anti-psychotics and anti-depressants are not the same thing.

400 compared to 33,955 is insignificant. That's 1.2% of patients taking any form of thyroid were on T3.

My levels are always 50 to500.. I'm under active size 6 and never feels well

I see you are new here. Welcome.

Please feel free to start your own thread to ask whatever you want.

Am not clear what levels you are talking about?

Been on T3 for nearly 30 years after having thyroid removed due to thyroid cancer. Funnily enough, had the op done in Dundee (in Tayside for all those who don't know!). So I might be one of the Tayside group. Feeling fine! According to my wife, I've just the usual mental problems of being a husband.

T3 has a much shorter half life in the body than T4, so T3 is used after thyroid removal so that they can test if the thyroid is regrowing (only 2 weeks off T3 prior to test, rather than about 6 weeks off T4). No GP has ever questioned my still being on T3 .... until now, as the price for 28 pills hits £100+. So costs £300+ a month for me to be on T3. Monopoly of supply in UK. Have another "interview" with the GP next month to see what the latest thought are.

T3 is the main hormone in the body which affects metabolism, T4 really doesn't do much (apart from converting into T3), so, all else being equal, T3 would seem to be a better hormone to take. But T4 much, much cheaper, which is where the main issue arises I suspect.

I bet the anti-psychotic increase was written mostly for sleep but clumped into the mental illness category. Wow I'm printing out this article. I love that the findings are protected by copyright

Understand about the copyright - but it is the precise wording and layout of the article rather than the findings as such.

It is, to me obviously, fundamental to find out WHY the increase in anti-psychotics - your suggestion should certainly be in the possibles list.

You may also like...