Mounjaro, weight loss and Levothyroxine

[HashBlue]

At the beginning of December I started taking Mounjaro to help with weight loss. I was at BMI 35 and struggling to lose weight despite improved result following an increase in levothyroxine dose

TSH of 1.2 range 0.27-4.2

T4 16.7 range 12-22

T3 4.1 range 3.1-6.8

Almost instantly I noticed some changes to my thyroid symptoms. I went from always cold to always hot, and my heart rate showed a marked increase (by 20 beats per minute). weight came off quickly (over 3 stone to BMI 24.5).

I had a review with GP as I felt a bit jittery and suspected I was over medicated, a blood test confirmed it

TSH < 0.05 range 0.27-4.2

T4 34.1 range 12-22

T3 10.1 range 3.1-6.8

I’ve reduced my levels and now waiting to retest, but continue to lose weight with Mounjaro, it seems to impact on thyroid symptoms. we know it has strong impact on certain hormone productions as it increases GLP production improving blood sugar control as it’s targeted for diabetics. But there hasn’t been any confirmed relationship with thyroid hormones.

Just thought I’d share in case anyone else is looking at using weight loss injections

I’m not aiming to lose much more weight and am trying to slow things down now to try and prepare for maintenance, it’ll be interesting trying to find a balance and seeing what happens in the future when I reduce dose or come of entirely

[Buddy195 Administrator]

Thank you for sharing your story HashBlue.

I hope that your ‘hyper like’ symptoms (from being over- medicated thyroid wise) pass quickly, with the reduced Levo dosage.

How much Levo were you taking in December 2024? How much have you been advised to reduce by?

I would advise anyone commencing weight loss medication to retest thyroid levels after 6-8 weeks and adjust medication accordingly.

[Sleepman]

Thanks for sharing.As you are only a year or so in, could it be a hashi swing as well as the Mounjaro?

3 stone is huge reduction, dose is related to weight somewhat.

[greygoose in reply to Sleepman]

I agree. And there's no way anyone could go from an FT4 of 16. 7 to 34.1 whilst still on the same dose without a Hashi's swing, even with the difference in weight. So, your weight-loss is, at least in part, due to that.

[HashBlue]

I was alternating between 75 and 50 in December and have moved to 50 per day 3 weeks ago, with improvements in symptoms quite quickly after dose change

[sparkly]

Thanks for sharing. It's good to know that you can still lose weight on mounjaro even having thyroid issues, and really appreciate you being honest about what has happened.Once you're settled on lower dose I'm sure you'll feel so much healthy and so much happier.

I know a lot of folk with thyroid issues will want to take it but be apprehensive. Me personally, I would if I needed to. I've spent far too many years doing myself damage by eating nothing, only to gain weight and further lower my metabolism.

[ThymeTime in reply to sparkly]

Agree with your last sentence so much. (I’m currently on Mounjara and trying to get my thyroid sorted out at the same time).

[HashBlue in reply to ThymeTime]

I hope it works for you too, it’s been great, I feel back to my old self pre menopause and hashimoto

[Reynards]

I’ve been on mounjaro for a year and have lost two and a half stone. I haven’t had to change my Levo dosage at all. Struggling sometimes with sickness and nausea but general feeling good on it.

[McPammy]

is it ok to take this weight loss injection/drug with a thyroid condition? I was informed people with thyroid disorders shouldn’t take it due to it causing thyroid cancer in the longer term.

When you were prescribed it were you questioned if you had a thyroid disease?

[HashBlue in reply to McPammy]

Yes I gave a full medical history before it was prescribed. My GP is aware and has no issues with me having the medication and is pleased with my progress. I was at greater risk of ill health through continued weight increase than through taking Mounjaro. Like all people taking it I need to monitor and report any side effects.

NICE don’t list it as a contra indication

GP practices are prescribing for morbidly obese people with diabetes with or without thyroid issues.

I considered the risks and chose to go ahead

[Judithdalston]

I’m hypothyroid and diabetic ( type 3c ie don’t produce insulin due to pancreas damage) and been interested in these various injectables for some time…I found best place for much information is the US site/ forum: Diatribe. Obviously started for support for diabetics but frequently highlight all these drugs and research coming out about them…have a look. I personally would think it’s weight loss that has affected your thyroid results.

[HashBlue in reply to Judithdalston]

Thanks Judith. I think it was the Mounjaro personally. A number of people using have noted impacts on their other conditions such as fibromyalgia, psoriasis, PCOS as well as diabetes. The changes to heart rate occurred within 2 days of starting on MJ and other symptoms gradually increased, I just thought they were MJ side effects until they got strong enough for me to recognise that it related to thyroid and arranged the blood test.

However I’m not aware of others having had the same reaction. I only know a small number of people of Levothyroxine and Mounjaro. Before I started my results were pretty good, but a lot of people struggle to get Gps the prescribe enough to get their TSH to 1, so they may only notice positive benefits if their starting point wasn’t so close to optimum.

Or it could all be coincidence and I may have just had a thyroid storm just as I started taking the meds 😊 I understand that’s possible too

[Judithdalston in reply to HashBlue]

Hi, I just went back to the DiaTribe site and looked up the bid trial on Tirzepatide( Mountjaro) with 2,500 participants…no mention of thyroid in ‘side effects’ though lots of things are not just BP, lipids, insulin etc from pancreatitis etc etc. Conclusion does suggest degree of ‘nutrient stimulated hormone pathway’ but obviously connected to obesity not thyroid. I don’t know whether the trial deliberately removed hypothyroids from the research, but with 2,500 I’d have expected some otherwise to be hypos!

[HashBlue]

I’ve not heard anything so extreme from the group that I’m in. However a number of people have had upset stomachs, particularly soon after a dose change. I did when moving from 2.5 to 3.75, but it was relatively mild, cramps and a strong desire to go to the loo rather than uncontrollable situation. But I’m glad I stepped up in smaller increments, going straight to 5 may have been a disaster. I chose to go up slower because I had a strong reaction with lots of appetite suppression and I didn’t want to struggle eating enough

[Judithdalston]

Out of curiosity later did more research: the cancer link to Mountjaro etc seems to be related to those who were hypothyroid as had thyroid removed in the first place due to cancer at site, not autoimmune hypothyroidism. If anything Mountjaro seems to be linked to under medication by Levothyroxine( and I presume T3 though not specifically mentioned) as digestion is slowed down so levo.does not get absorbed as expected. The GLP-1 part of the Mountjaro regularly lowers BP and subsequently rises HR; as someone who is having problems with BP/HR as a result of Long Covid I can fully understand this weird ‘high/low, low/ high’ cardiovascular reaction, but again could linked to your lost weight.

[HashBlue in reply to Judithdalston]

I did some more research myself and all I could find factually about thyroid cancer risks related to tumours developing in mice and rats on very high doses of the drug. I found none relating to humans, but they warn about it to ensure people are monitoring for symptoms such as thyroid swelling