Thyroid UK

Erectile Dysfunction with Levo Increase

One of the interesting side effects as I've increased my dose of Levo (from 75mcg to 100mcg each day) has been that my libido has taken a major hit and more to the point I hardly ever have an erection any more.

Seems strange to me that an increase in levo would adversely effect male hormones like testosterone etc. but I can't see an obvious link.

Does anyone else here have any experience of this phenomenon ?

Recent TSH was 1.9 and Free T4 was 19.

3 Replies


It seems hyper and hypo thyroidism can cause this to happen.

So could you be over medicated with this increase ?

Were the bloods taken when on 75 or 100 T4 ?

Do you know your testosterone levels ? If quite low this may have tipped into "far to low".

It is important to measure heart rate, blood pressure and temperature at set points in the day to see how the metabolism is responding to the increase in T4. Sometimes we don't know if we are being over medicated and so these signs are important to monitor.

Another possible cause could be the demand placed on the adrenals from the extra thyroid. Thyroid hormones works in tandem with cortisol and so if you supply more thyroid you will require more cortisol. The body may not be up to supply this energy source and so it will divert dhea production to go towards the greater cortisol demands. DHEA is the adrenal hormone which is turned into testosterone. So testosterone may drop a bit.

I can't say for sure what is happening behind the scenes, but hopefully this info can help build out your picture.


Thanks for the detailed response.

The results were from 75 mcg as I only increased to 100 mcg quite recently but with a TSH of 1.9 I didn't think it would push me over . Plus my heart rate is on average 58 - 63 BPM so I know I'm definitely not hyper .

Recently ordered male hormone tests from blue horizon so hopefully that will help clarifying things.


It is recommended that a TSH of 1 or lower may alleviate our symptoms better. If you get a Free T3 blood test taken , that would give an idea how much T3 you are converting from T4 (levothyroxine). Levothyroxine is the inactive hormone and has to convert to T3 which is the only Active hormone required in our billions of receptor cells. It should be towards the top of the ranges as should FT4. if you can get both done and post results with the ranges.

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