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Pregnant, Low free T4, very low TSH
I am 25 weeks pregnant with twins and have Hashimotos, which has been untreated due to thyroid levels in the normal range for years.  My OB referred  me to an Endo because my most recent labs showed low levels for TSH & Free T4, as follows:

TSH - 0.037 (reference range .4 - 4.5)
Free, serum,  T4 - 0.69 (Reference range 0.82 - 1.77)
Free, Serum T3  - 2.3 (reference range 2.0 - 4.4)

I am very worried since untreated hypothyroidism can cause cognitive problems in the unborn babies.  The endo looked at my labs and said that Free T4 levels are not that accurate during pregnancy and diagnosed me as hyperthyroid and said I didn't need any medication.  She drew more blood, however my next appointment isn't for 1 month since she is going on vacation.  Every site that I have go to online says that low TSH and low T4 could indicate secondary hypothyroidism, not hyperthyroidism.  I have some symptoms of being hypothyroid, such as feeling cold, and I also had lost a lot of hair prior to getting pregnant.   I am wondering why the endo didn't even consider secondary hypothyroidism caused by the pituitary or hypothalmus when she was diagnosing me.   What labs test are used to diagnose secondary hypothyroidism?  Can I really be hyperthroid just due to the low TSH level?

I am confused and would love any help you can give.

Thanks!

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My opinion is that your diagnosis is a lot better than your doctor's.  Not only is your FT4 below range, but FT3 is in the very low end of the range.  Not only that but both ranges are also far too broad.  I say this because the ranges for FT3 and FT4 have never been adjusted as was done for TSH over 7 years ago.  As a result, the low end of the range for each is far too low and is an apparent reason we hear from so many members that have their "Frees" in the low end of the ranges and continue to have lingering hypo symptoms.  

It was good that your doctor at least tested FT3 and FT4, instead of just relying on TSH.  TSH is affected by so many variables that it is inadequate as a diagnostic.  It is even less reliable in cases like yours, where a low TSH along with low FT3 and FT4 indicate the need for further testing of the hypothalamus/pituitary functions.  A low TSH does not automatically mean that you are hyper, unless accompanied by hyper symptoms and excessive FT3 and FT4 levels--certainly not the case for you.  

Hopefully other members will give you the benefit of their personal experience.  Personally I would not wait one day.  I would try to find a good thyroid doctor by asking members to recommend one in your area.  If that doesn't work, we'll come up with some other suggestions.  
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Thanks for the advice.  I am trying to find another endo now!
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