I have lost 3 stone using Mounjaro over the last 8mths and recently had an episode of Tachycardia, lasted about 10 mins. A & E couldn't find anything wrong, GP tested thyroid and found I had a TSH just in range ( O.34 approx) but T4 was over range, 28 I think she said. Cause found she believes, Levothyroxine needs reducing due to weight loss. I have been referred for cardiac diagnostic to rule out any cardiac cause.
I wear an apple watch and at the time pulse went to 179 which more or less agreed with my BP machine which I grabbed when I started feeling off. BP was not raised, a little low if anything. Prior to and since my pulse is in normal ranges for me, any where between 60 and 80 resting with a couple of dips into the low 50's.
Highest T4 when tested over the years was 19 and except when taking NDT in the past, everything is always in range. I can't find any info online that links raised T4 with tachycardia; is too much circulating T4 a likely culprit? Are there any other symptoms that link to raised T4?
I'm not mega concerned but thank you in advance for any info
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sue_b
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current dose 125mcg- was on 150mcg alternating with 125mcg for 4yrs, weight for most of that time 21st. So have cut out between 75-100mcg per week.
I still weigh 18 stone and my dose wasn't increased in recent yrs, when I queried this with my endo, because I had gained and felt crap, he said it was nonsense that dose should be weight dependant GP also commented that I was on a high dose. I calculated I needed 175mcg at my highest weight.
Brand varies depending on what they have in, currently, and usually, Mercury Pharma.
I always book blood test first thing before taking morning dose but had no choice with the last NHS one, 1.30pm , no levo since morning before.
Private test last week, no levo since day before, about 5 wks after reducing dose TSH 1.44 ; T3 4.5; FT4 19.2; all usual ranges. I live in Wales now so no online access to blood results, everything was fine though, GP very happy; I'll need to get them to print out.
I have just come across a mention of 'increased thyroid activity' being a less common cause of tachycardia but I never had any issues in the past when taking NDT.
You need to test both TPO and TG thyroid antibodies tested at least once to see if your hypothyroidism is autoimmune
About 90% of primary hypothyroidism is autoimmune thyroid disease, usually diagnosed by high TPO and/or high TG thyroid antibodies
Autoimmune thyroid disease with goitre is Hashimoto’s
Autoimmune thyroid disease without goitre is Ord’s thyroiditis.
Both are autoimmune and generally called Hashimoto’s.
Significant minority of Hashimoto’s patients only have high TG antibodies (thyroglobulin)
NHS only tests TG antibodies if TPO are high
20% of autoimmune thyroid patients never have high thyroid antibodies and ultrasound scan of thyroid can get diagnosis
In U.K. medics hardly ever refer to autoimmune thyroid disease as Hashimoto’s (or Ord’s thyroiditis)
Very important to test vitamin D, folate, ferritin and B12 at least once year minimum
Low vitamin levels are extremely common when hypothyroid, especially with autoimmune thyroid disease
Recommended that all thyroid blood tests early morning, ideally just before 9am, only drink water between waking and test and last dose levothyroxine 24 hours before test
This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)
Private tests are available as NHS currently rarely tests Ft3 or all relevant vitamins
If you normally take levothyroxine at bedtime/in night ...adjust timings as follows prior to blood test
If testing Monday morning, delay Saturday evening dose levothyroxine until Sunday morning. Delay Sunday evening dose levothyroxine until after blood test on Monday morning. Take Monday evening dose levothyroxine as per normal
IMPORTANT......If you are taking vitamin B complex, or any supplements containing biotin, remember to stop these 3-5 days before ALL BLOOD TESTS , as biotin can falsely affect test results
In days before blood test, when you stop vitamin B complex, you might want to consider taking a separate folate supplement (eg Jarrow methyl folate 400mcg) and continue separate B12 if last test result serum B12 was below 500 or active B12 (private test) under 70
I have poor conversion due to Snp's and MTHFR C677T issues, both sets of anti-bodies, tend to go low in VIT D, B12, and folate if I don't supplement.
My experience of reducing levo is that my levels reduce quite rapidly so I tested a little earlier than my GP intends so but I will have some info about the effect of reducing the dose. I don't have the money for private tests/medication so rely on NHS. I plan to ask for full results of what they tested- she was more interested in how good my liver function, cholesterol and Hba1c were, basically because of the Mounjaro effect. New country/Gp practice/GP so I will take it steady with them for the moment.
Do you have any info about high T4 causing tachycardia?
Increased heart rate can be quite a common effect of mounjaro. I am on it, and am experiencing exactly that.
I don't get palpitations or anything like that, but my resting heart rate has gone from around 90bpm to around 110bpm, which obviously isn't great. I'm on T3 only, so I'm a little bit loathe to go to the GP as I think they'll blame it on that rather than realising it's a common side effect of mounjaro.
I'm on holiday right now, but going to check again when I'm home then contact my prescriber if still high to see what they suggest.
Hi, yes, I had heard that heart rate can increase when on MJ which perhaps should be expected if it is reducing the need for thyroid meds whether that is due to weight loss or better liver function/conversion. If you are not monitoring these things you might never know there were any changes, so there will never be a definitive answer except on an individual level.
I think I would be getting a review if my heart rate had increased consistently, maybe think about getting your t3 tested privately? There are many more experienced than me on this forum who could comment on that.
My issue was a sudden very high spike which my Apple watch recorded and my BP machine confirmed. Even with that evidence the hospital didn't quite believe that what I was telling them was accurate. I don't really believe that an assumed consistently high T4 would cause a random spike, once. I doubt an answer is out there
I am being referred for a 2 day ECG test to rule out any persistent issue but I doubt they will find anything. I guess we are all different and the effect of mounjaro highlights that for me. I get constipated my daughter has the opposite. All the uncertainty is the price we pay for finally breaking the strangle hold and losing some weight
I had a very similar situation as yourself after my TT. I was dosed on very high T4 for suppression purposes. I struggled with palpitations to the point of being afraid to leave the house. I later learned that while my FT4 were high my FT3 was very low. Muscles need T3 as does the brain and Especially the Heart. The Heart has a Large Receptor sights and is a muscle and needs T3. I don't understand why Dr's are so negligent when it comes to T3. In my case instead of lowering a bit my T4 and adding the very much needed T3 they just raised my T4. In addition having low Iron and Ferritin is a large contributor to heart palpitations. I hope you Get Sorted out very soon.
Hi, thank you for your reply, so maybe my GP is right. I know they don't usually check T3 but it is possible they did due to high t4 so I will ask her.
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GP also commented that I was on a high dose. I calculated I needed 175mcg at my highest weight.
High TSH~normal range Free T3, T4
What is the relationship between Free T3 and Free T4 and TSH?
Switching from a NdT to bioidentical t4 and t3
getting it off my chest..another Dr.who says my high HR is too much levothyroxine! 
