Metformin/ thyroid test

[Trelissa]

I am so sorry I can't remember this.I no that the thyroid function text is knocked out of kilter with metformin. I am preparing a yellow card report for the MHRA regarding this and I want to get my facts right. What are the facts around this?

(Yellow card is the tool used to report side effects of medication-patients can now do this)

Thank you for any help.

[SlowDragon Administrator]

Metformin can lower TSH

cureus.com/articles/50564-e...

But it doesn’t appear to affect tolerance of taking levothyroxine

So not sure yellow card is an appropriate response

[Trelissa in reply to SlowDragon]

E guidance regarding I was taking metformin with hyperthyroidism symptoms, but it did not show up in blood tests until I came off it. Metformin also lowered my B12, and was responsible for causing hyperlactatemia. I know that if you have diabetes mellitus or PCOS it can affect the thyroid function test (I think it is) it had hidden graves disease, there are additional tests you can do in order to identify if the person taking metformin has thyroid issues. NICE guidelines does ot give any recommendations regarding this. I just cannot remember the details

[SlowDragon Administrator in reply to Trelissa]

Anyone on Metformin should have B12 levels tested regularly

gov.uk/drug-safety-update/m...

Also can lower magnesium levels

cdnsciencepub.com/doi/abs/1....

[grumpyold]

I have been on levothyroxine for 23 years and T4/T3 combo for 2 years. I was also put on Metformin 8 years ago. Metformin works along the HP axis and makes the TSH appear suppressed. The FT4 and FT3 remain unaffected.

Like SlowDragon says, I don't see why a yellow card report would be appropriate.

[Trelissa]

Thank you so much

[Trelissa in reply to Trelissa]

The yellow card is there to help identify and understand side effects, and rely on people sharing their experiences of suspected side effects, including those that have been acted upon. B12 and lactate already have guidelines in place, but ensuring up to date reporting ensures they are kept up to date. However I especially concerned that those with DM and/or PCOS do not have the additional FT3 and FT4 as a NICE guideline

The MHRA are one of the routes that can flag this. I have been through hell and back because I had undiagnosed Graves for 6 years, which was only picked up after I was taken off metformin due to cancer. I cannot find signs for this being campaigned for, contacting mhra and nice is my first port of call as I am familiar with their processes.

That was behind my thinking