Avatar universal

False Negative to TSH possible?

I have several symptoms of Hypo......Weakness, unmotivated, inability to lose weight despite exercising and diet, can get cold easier than I use to, My mom, Grandmother and Niece all have Hypo.  But the blood tests always show me normal most recent at 3.00  (0.45-4.50)  being considered normal.  I'm going to the PCP next week for my yearly and asking for the test again.  I just have too many of the symptoms and with the family history.  I can't sweep it under the rug anymore.  I hear STRESS can effect your hormones.  I have severe stress in my life with both my son and husband having Myotonic Muscular Dystrophy which includes cognitive issues, Cardio, lung, GI and numorous others.  My husband is in and out of hospitals with close death calls that I can't even count.  So STRESS is in my life never knowing if this hospital stay is the last one.  And I care for my 88 yr old mom.  I need to be able to function.  I'm not depressed although I guess I have every reason I just feel unmotivated until a crisis hits then I'm "Superwoman" than after I crash.  Thanks In advance.
4 Responses
Avatar universal
TSH is a pituitary hormone that is affected by so many different things that at best it is only an indicator to be considered along with more important indicators such as symptoms and also levels of the biologically active thyroid hormones, Free T4 and Free T3.  There are two basic types of hypothyroidism: primary which is Hashimoto's Thyroiditis related, and central which is a dysfunction in the hypothalamus/pituitary system that results in inadequate TSH to stimulate the thyroid gland to produce needed hormone.

So your TSH result is not conclusive that you are not hypothyroid.  With all those symptoms and family history of hypothyroidism, you need to test further.  Specifically you should request to be tested for Free T4 and Free T3 (not Total T4 and Total T3), so be sure they test for the Frees.  Also, test for Hashi's antibodies.  Those tests are TPO ab and TG ab.  Since hypo patients are so frequently too low in the range for Vitamin D, B12 and ferritin, those should be tested also.  If the doctor resists, just emphasize all those symptoms you have that can be related to hypothyroidism and your family history and that TSH testing alone is not always conclusive.  

When you have results, please post them, along with reference ranges shown on the lab report and we will be glad to help interpret and advise further.
Avatar universal
I agree with Gimel.  I fought my PCP for 7 YEARS & all he would ever test was the TSH.  Mine was normal, too.  I ended up circumventing the system & got the proper testing like Gimel mentioned and, yep, my Free T4 & especially my Free T3 were low.  I *was* hypothyroid like I'd been maintaining & all my doc had wanted to do was push antidepressants.  My new doc got me started on meds & I've started to feel better.  Please, for your own health, do NOT let your doc convince you that a normal TSH is the be all & end all of thyroid diagnosis!!!  If he balks at ordering it, there are testing kits from places like ZRT lab that you can get & do in the comfort of your own home with just a simple prick of your finger.  Most insurances won't pay for them but, hey, getting the right diagnosis & the right medication is WELL worth a couple hundred dollars out of pocket.
1756321 tn?1547095325
TSH is one of the markers of thyroid dysfunction. It isn't the be all and end all of tests but a TSH over 2.5 is a red flag.

"In the future, it is likely that the upper limit of the serum TSH euthyroid reference range will be reduced to 2.5 because >95% of rigorously screened normal euthyroid volunteers have serum TSH values between 0.4 and 2.5" -  National Association of Clinical Biochemistry.
Avatar universal
When you really think about it, what is a TSH test supposed to represent?  Scientific evidence shows that it does not correlate well with either Free T4 or Free T3, much less with symptoms.  When already taking thyroid med, TSH is almost useless as an indicator of thyroid status.  About the only value of TSH is to distinguish between primary and central hypothyroidism.  So why is it that we all have to spend so much time hassling with doctors about the meaning of a TSH test?  

Even if an upper limit of 2.5 were adopted (which will never happen), what about the 5% that would be outside the limit?  Should they still be ignored and told they couldn't possibly have a thyroid problem?  Would the other 95% be totally without any thyroid problem?  I don't think so.  Would a patient with a TSH of 2.51 be diagnosed as hypo and treated, but a patient at 2.50 be denied treatment?  Obviously ridiculous.  

Patients don't go to doctors saying, "I think my TSH is too high."  They go to the doctor because their tissue thyroid levels have dropped low enough that their body functions have begun to slow down, and they have resulting symptoms of being hypothyroid.  So what we would really like to know is tissue thyroid levels, but I don't think patients would appreciate tissue samples being taken from various parts of their bodies each time they went in for evaluation.  So, the best approach to trying to assess tissue thyroid levels at present is to evaluate other surrogate variables as close as possible to tissue thyroid levels, so that there is good correlation and thus the opportunity for effective control.    

Just upstream of tissue thyroid, for potential surrogate measures we have the biologically active thyroid hormones, Free T4, Free T3, and perhaps Reverse T3.  Potential downstream surrogate measures include basal body temperature, resting metabolic rate, tendon reflex and symptoms. From that list of potential surrogates, at present the best choices are symptoms, and Free T3, Free T4, and possibly Reverse T3.  There are significant efforts currently to correlate tendon reflex with thyroid status, but it is a work in progress.  And of course there is scientific evidence that Free T3 correlated best with hypo symptoms while Free T4 and TSH did not correlate at all.  

The reason TSH does not warrant consideration as a surrogate for tissue thyroid levels is due to all the levels of potential variability between tissue thyroid levels and TSH, including the rate of transport of serum T4 and T3 into the cells, the conversion of T4 to T3 and RT3, the hypothalamus response to a given level of serum T4 and T3 and the corresponding output of TRH, the pituitary response to TRH and the output of TSH.  So depending on how you count them, there are 4 to 5 levels of variability between tissue thyroid and TSH, with each level affecting the correlation between the two.   There is no way that a knowledgeable statistician would ever resort to TSH as a surrogate for tissue thyroid levels, due to expected poor correlation between tissue thyroid and TSH, and that has been proven true with valid data many times over.  

If you want to diagnose a potential hypothyroid patient you have to use surrogate measures that correlate with tissue thyroid levels.  That certainly is not TSH.  At present the best approach to diagnosis and treatment of a potential hypothyroid patient is clinical, based on symptoms, and levels of the biologically active thyroid hormones, Free T3 and Free T4.  That is how good thyroid doctors do it.  
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