Low TSH just before IVF cycle

[sare68]

Hello Dr Lupo

I am 40 years old and about to have a frozen embryo transfer next week (Wednesday). This is a natural cycle - no medication except some luteal phase support.

My TSH is very low and I have some concerns I hope you can allay.

I have had hypothyroidism for a year. My GP, who manages my dosage, increased my dose of thyroxine 6 weeks ago (to 650 mcg a week) as my TSH was increasing and my T3 and T4 dropping. I got test results back yesterday that show my TSH is .03 (.3 - 5), my T4 18.8 (9 - 19) and T3 4.7 (2.6 - 6).

My concern is that the low TSH may affect my hormones in some subtle way and compromise the success of my frozen embryo transfer.

However, my hormones appear to be fine.... blood tests show I am ovulating today. My luteal phase last cycle (a non-IVF cycle) had high and sustained temperatures and lasted 13 days.

My usual fertilty specialist is away and her replacement did not seem certain of whether such low TSH  might pose a problem. Under the guidance of my GP, I am adjusting my dose to get my TSH up a little - but not too dramatically, so I imagine it may take a couple of weeks to get a change of any significance.

I do hope it's okay to go ahead with the transfer next week.

Thank you in advance for any advice you might be able to offer.

Sare

[Mark Lupo, M.D.]

The low TSH in this setting has not been proven to decrease fertility but I agree with a slight dose decrease to let it come back to the low-normal range.

[sare68]

I should add that I have no symptoms of hyperthyroidism at all. Actually I feel really good!
And, obviously, that 650mcg a week was spread through the week! (Actually I was on 600mcg one week and 650 the next). To alter my dose, I had a day without thyroxine yesterday and have reduced the dosage to 600mcg each week. Does that sound like a good plan (ie not too fast a reduction) in light of the transfer next week?
Sare

[Super_sally888]

Hi Sare,

My doctor adjusted my thryoid levels for FT3 and FT4 to be high normal range before I got pregnant last year.   I then got pregnant and had a successful pregnancy and now have a healthy 5 mo old.

if you do get pregnant, it will be important to monitor your thryoid levels closely.  The demand for thyroid hormone increases significantly during pregnancy, even in the first weeks.

From my own understanding your current levels should be ok.

Good luck with your ivf cycle.

[sare68]

Thanks very much Dr Lupo - your comments reassured me. Thanks too, Super Sally for sharing your experience.

The good news is that our frozen embryo transfer worked. I am pregnant! Of course it's early days but I am quietly optimistic. I will have my TSH, T3 and T4 tested on Tuesday to see what's happening and, under guidance of my GP, will adjust as necessary.

Thanks again.

[Super_sally888]

Congratulations on the pregnancy. Wishing you a smooth and easy pregnancy.