Is Free T4 important when trying to conceive

[LJO91]

Hi, I’ve been trying to get my TSH levels down to below 2.5 since January so that it is safe to try for a baby. Got my results today and they are 1.62 so I can finally start trying again. However I noticed on my results that my free T4 is 21.6 pmol/L. It was always between 14 - 15.5 previously. Lab range is (12.00-22.00) so it is still within range only just, but should I be concerned that it’s rising? And is there a certain level this needs to be for safe pregnancy/trying to conceive?

[greygoose]

The problem is that doctors assume that if your TSH is under 2, then your Frees are going to be in-range, and if they're in-range, they have to be perfect. I would think that with a TSH of 1.62 and an FT4 of top of the range, you probably have a conversion problem - i.e. you don't convert T4 to T3 very well.

T3 is the active hormone, and T4 is more or less just a storage hormone. So, the FT3 is the most important number, but they never test it! Nothing is ever said about where your Frees need to be to conceive, just the TSH. But, the TSH itself has nothing to do with conception - or carrying a baby to term - it's just a vague indicator of thyroid status.

On the other hand, you do need a good level of T4, because it's T4 that crosses the blood/placenta barrier, and in the early months, the baby is entirely dependant on its mother's thyroid hormone for brain development. So, you'll probably be ok on that score. But, a good level of T3 is also necessary to keep the mother well. Might be a good idea to get full thyroid testing privately, if you can.

[SlowDragon Administrator]

Very important to test vitamin D, folate, ferritin and B12 too, especially when considering TTC soon

Low vitamins are extremely common, especially if you have autoimmune thyroid disease also called Hashimoto's

Have you had both TPO And TG thyroid antibodies tested?

Obviously you need FT3 tested at same time as FT4 and TSH

[SlowDragon Administrator]

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if Thyroid antibodies are raised

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and fasting. This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

Last Levothyroxine dose should be 24 hours prior to test, (taking delayed dose immediately after blood draw).

Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies or all vitamins

thyroiduk.org.uk/tuk/testin...

Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have special offers, Medichecks usually have offers on Thursdays, Blue Horizon its more random

What vitamin supplements do you currently take?

If you are taking vitamin B complex, or any supplements containing biotin, remember to stop these 7 days before any blood tests, as biotin can falsely affect test results

endo.confex.com/endo/2016en...

endocrinenews.endocrine.org...