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Thyroid UK
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Testosterone and levothyroxine

Does testosterone replacement therapy (TRT) interfere with levothyroxine?

I've had 9 months of TRT injections with the medication (Nebido). My TSH levels have risen from 0.5 (range 0.3-4.2 ulU/ml) to 1.7 then to 2.0. My fatigue and dull headache is back.

I donated blood yesterday due to high red blood count and high haemaglobin, under my Endo's guidance.

My Vitamins were tested and are all ok. Free T3 was 4.4 (2.8-6.8 pool/L range) and Free T4 was 15 (12-22) I read here that this is low

Is there a link between TRT and TSH levels?

I've been taking 100 mcg levo for 1-2 years. My Endo is adamant that 2.0 is ok and binned to increase. I've read her that TSH should be at or under 1.0. Should I add 25 mcg and take 125 mcg?

Could it be the colder weather necessitating a higher daily levo dose during the winter?

All connects gratefully received. Thank you in advance and for all your good work.

4 Replies

Check your estradiol (E2) levels. When you take too much testosterone, it can convert to estradiol. Estradiol raises thyroid binding globulin (TBG), which then lowers your free thyroid levels. This should raise your TSH.

You are probably taking too much testosterone at once if you had to donate blood. This will lower your ferritin, which you need for thyroid hormone supplementation. While raising your levo could help somewhat, I think it would be easier to lower your TRT dose and to take less more often. Have you heard of subcutaneous dosing? Men are able to take much smaller doses that way twice a week, which greatly reduces their estradiol levels.

More on TRT and thyroid: tiredthyroid.com/mens-hormo...


What is the best tests to have re testosterone etc when on t3 and t4 please? As I'm on hrt and identify with this some what, but haven't had a test re the hrt I'm taking, so no idea what my blood work is like or interaction witht3 or t4... Thanks Jo


If you scroll down on this page, there's a comprehensive list of tests: tiredthyroid.com/what-labs....

1 like

Thanks.. Didn't want to gatecrash but I haven't seen too many posts with the links with folk near menopause etc with thyroid issues... If you split the question and go to a menopause forum they don't know much re thyroid and vice versa... So thanks...


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