# Thyroxine and oestradiol interaction



## Pookychops (Aug 3, 2010)

Hi,

I'm hypothyroid and take 100mg thyroxine daily. I was diagnosed with graves disease age 10 and after years of medical management I was treated with radio iodine and have been hypothyroid since age 17.

I have just started taking oestradiol 6mg daily as part of my FET cycle. I have been told that this could interfere with the absorption of thyroxine and to have my thyroxine levels monitored more closely. However, no one has said how often. I thought the hospital was going to write to my gp to tell him but they only told him to monitor it more often. I am also sniffing buserelin twice daily.

How long would it take for my thyroxine levels to be impacted by the oestradiol? Are we looking at weeks or months?

I did take clomid before and that led to me needing more thyroxine after about 4 months - although I didn't realise and went quite hypo before it was picked up. The docs then told me that there was no interaction between the two drugs. My thyroid does seem to be quite sensitive though and stress can kick start a bout of hyperthyroidism.

My gp has given me some blood test forms to use when I need to, but it would be useful to have an idea as to when to time the next test and a bit more info.

Thanks

Liz


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## Mistletoe (Holly) (Jan 1, 2007)

I have checked in Stockley's Drug interactions and there is a potential interaction between the two.
It does say about women starting or stopping HRT that thyroid function should be monitored ''within months'' of any changes to treatment.

The interaction with thyroxine is more complex than absorption and involves binding proteins in the blood made by the liver.

I am not an endocrinologist, but I suggest that you perhaps get it checked after about 4 weeks whilst doing fertility treatment/pregnancy. Do discuss it with your own doctor.


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## Pookychops (Aug 3, 2010)

Many thanks. I spoke to a nurse at the unit and she recommend every four weeks too. I think the main problem is that the unit told the doctor to monitor more often but as I only have it checked annually he wasn't sure how often that would be.


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