Low TSH in blood test

amooraxo · November 2014

I just got my first blood/urine test results back today and will discuss with my doctor during my next appointment at 12 weeks (8th December) and everything is shown to be within the normal range except for my TSH levels.

My result was 0.17 uIL/mL

Normal range per the results sheet: 0.55 - 4.78 uIL/mL

My FT4 was normal at 1.46 ng/dL (range 0.89 - 1.76 ng/dL)

I was a little freaked out and started googling a ton thinking my thyroid wasn't working or something but then learned that TSH numbers are actual opposite from what they seem. A high number indicates hypothyroid while a low number means hyperthyroid. I also read that hCG and estrogen can cause TSH to be lower during the first trimester.

Does anyone else have results like these or done any research on TSH & FT4 numbers?

jbartsy · November 2014

Same thing happened to me (oddly enough I think my numbers were almost the same as yours), and my doctor wasn't concerned. The levels should go back to normal when HCG levels start going back down. I'm sure that your doctor will let you know if you have reason to worry.

amooraxo · November 2014

Thanks @jbartsy ... that makes me feel better.

The nurse wasn't able to tell me anything, other than they would test again in 4 weeks. So hopefully when I'm out of the first trimester they will normal out a bit.

Anyone know when baby's thyroid starts working on it's own? I thought it was the end of the first trimester but I've done so much reading my mind is on overload!

chloepolk · November 2014

I have hypothyroid and since getting pregnant my levels have been all over the place. My doctor has just told me that while I'm pregnant I'll have to be watched l. while your tsh levels were .17 mine were a 64.7. He said its normal to be a little off but because I already have hypothyroid it goes way off and can threaten the development of the fetus. Your doc will alert you when it gets too off

xbrandix · November 2014

My TSH just came back being 4.76!! I've been losing a lot of my hair and my doctor just put me on Levothyroxine. Hoping everything gets better soon! /: I wish you the best too!

amooraxo · November 2014

Thank you @pickles26 ... that's what I figured about the ranges. I really wish the nurse would have told me that... would have saved me from the mini panic I had about something being off.

Wishing both of you ladies @chloepolk & @xbrandix the best and hopefully your doctors can help manage things-- I know it's scary to have anything even slightly abnormal

amooraxo · November 2014

Found this online-- may be helpful for others with questions regarding their TSH numbers.

Thyroid Stimulating Hormone (TSH)

Units	Nonpregnant Adult	First Trimester	Second Trimester	Third Trimester
µIU/mL or mIU/L	0.34 - 4.25	0.6 - 3.4	0.37 - 3.6	0.38 - 4.04
mU/L	0.34 - 4.25	0.6 - 3.4	0.37 - 3.6	0.38 - 4.04
mIU/L		0.1 - 2.5 *	0.2 - 3*	0.3 - 3*

*References ranges recommended by the American Thyroid Association if trimester-specific reference ranges for TSH are not available in the laboratory.

ELEVATED TSH:
Some causes of elevated TSH include primary hypothyroidism (Hashimotos thryroiditis), TSH secreting pituitary tumor, thyroid hormone resistance, insufficient T₄ therapy for hypothyroidism, adrenal insufficiency, iodine, lithium, and antithyroid drugs.

When maternal TSH is elevated, measurement of serum FT4 concentration is necessary to classify the patient's status as either subclinical (SCH) or overt hypothyroidism (OH). SCH is defined as a serum TSH between 2.5 and 10 mIU/L with a normal FT4 concentration. Women with a TSH concentration above the trimester-specific reference interval with a decreased FT4, and all women with a TSH concentration above 10.0 mIU/L irrespective of the level of FT4 are also considered to have OH. [3]

LOW TSH :
Some causes of low TSH levels include, hyperthyroidism (Graves' disease), stimulation of the TSH receptor by hCG (first trimester of pregnancy, hyperemesis gravidarum, molar pregnancy/choriocarcinoma), exogenous thyroid hormone, thyroiditis, an autonomous thyroid nodule, dopamine, glucocorticoids, secondary hypothyroidism.

References:

1. Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009 Dec;114(6):1326-31. PMID:19935037
2. Brent GA.Maternal thyroid function: interpretation of thyroid function tests in pregnancy.Clin Obstet Gynecol. 1997 Mar;40(1):3-15.
PMID: 9103946
3. Stagnaro-Green A, ert al. American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum.Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011 Oct;21(10):1081-125.PMID .21787128

amooraxo · December 2014

I agree @pickles26 and I've noticed that the "normal range" for pregnancy has varied and changed a lot. I'm just hopeful that everything is good and with my next blood test things will be looking good... or more "normal".

Low TSH in blood test

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