Validity of TSH level to diagnose hypothyroidism

[TheSeanieB]

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[rokshana]

When a patient is presenting with symtoms of hypothyroidism, what should should be given more weight in their treatment, symptoms or their TSH levels? Also, does evidence of CNS ischemia weigh into the validity of the TSH level? If so, can it still be given some merit clinically and how much? Can't find any literature on this topic. Thanks.

if you are diagnosing, then the TSH (if its abnormal) shouldn't stand alone...you need a Free T4 and maybe a Total T3 to see if there is any issue...if the levels are all normal , then the symptoms m/l are not relates to the thyroid....remember the symptoms associated with hypothyroidism are non specific...other things can cause the symptoms and those avenues need to be investigated as well.

if you are monitoring a person on levothyroxine, then TSH is enough to make adjustments to the dose without the FT4 (but every case is different, so there may be a role for getting the FT4 as well)

 

[surge55]

When a patient is presenting with symtoms of hypothyroidism, what should should be given more weight in their treatment, symptoms or their TSH levels? Also, does evidence of CNS ischemia weigh into the validity of the TSH level? If so, can it still be given some merit clinically and how much? Can't find any literature on this topic. Thanks.

it's funny you ask this; I had a patient with constipation, cold intolerance and depression. I thought for sure she had hypothyroidism, but her TSH is only 0.86. Given that it's so low, I won't even check a T4. she may just have all these symptoms separately and in medicine that is definitely possible. so I'll treat her constipation with stool softeners and treat her depression with an SSRI.

 

[HelpPleaseMD]

it's funny you ask this; I had a patient with constipation, cold intolerance and depression. I thought for sure she had hypothyroidism, but her TSH is only 0.86. Given that it's so low, I won't even check a T4. she may just have all these symptoms separately and in medicine that is definitely possible. so I'll treat her constipation with stool softeners and treat her depression with an SSRI.

I would still get Free T4s. What if the patient had primary autoimmune hypothyroidism?
you may never know

 

[jdh71]

it's funny you ask this; I had a patient with constipation, cold intolerance and depression. I thought for sure she had hypothyroidism, but her TSH is only 0.86. Given that it's so low, I won't even check a T4. she may just have all these symptoms separately and in medicine that is definitely possible. so I'll treat her constipation with stool softeners and treat her depression with an SSRI.

While old people get cold, depressed, and constipated all the time, you might as well get the free T's.

This is internal medicine after all.

 

[rokshana]

it's funny you ask this; I had a patient with constipation, cold intolerance and depression. I thought for sure she had hypothyroidism, but her TSH is only 0.86. Given that it's so low, I won't even check a T4. she may just have all these symptoms separately and in medicine that is definitely possible. so I'll treat her constipation with stool softeners and treat her depression with an SSRI.

what's your reference range? AFAIK, a TSH of 0.86 is...normal...not really a need to check a FT4...its not her thyroid...

if one is suspecting hypothyroid, a normal TSH effectively rules that out....if the TSH is HIGH then you need to do FT4 (and maybe TT3) to see if there is any evidence of subclinical hypothyroidism...treating or not treating subclinical hypothyroidism is subject to a number of factors...if they do have subclinical hypo, it would be a good idea to get TPO antibodies...those who are positive have a increased risk of developing over hypothyroidism at some point.

 

[rokshana]

While old people get cold, depressed, and constipated all the time, you might as well get the free T's.

This is internal medicine after all.

yes, but not always because of the thyroid...TSH is normal, don't need the FT4...but it inpt IM so prolly will get a bunch of labs most of which won't change medical decision making...just makes people feel better...

 

[surge55]

While old people get cold, depressed, and constipated all the time, you might as well get the free T's.

This is internal medicine after all.

she is 30 actually.

you could argue TPO antibodies, but I don't see how free t4 is going to help, esp when her TSH is so low with reference range of 0.5 to 4.5.

Her symptoms are the least specific to hypothyroidism. depression, constipation, and cold intolerance are very very common. also, she has no weight issues, no muscle aches, no issues with her periods, no chronic headaches, no goiter/nodule, normal reflexes, no cholesterol issues.

I just don't want to get an expensive assay or assays just to completely rule out something that TSH does well on it's own.

 

[jdh71]

yes, but not always because of the thyroid...TSH is normal, don't need the FT4...but it inpt IM so prolly will get a bunch of labs most of which won't change medical decision making...just makes people feel better...

Sure. And all those labs occasional find pathology.

If you're going to send the TSH looking for thyroid problems based on clinical suspicion because of symptoms and not screening may as well send the T's

 

[TheSeanieB]

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[rokshana]

Sorry I should have included more info in my question. If the pt has had Hashimoto's for the 8 years, has been on a constant replacement dose of 75 mcg for the last 7 years and has not been managed (no TSH checks), now presents at the ER with a TIA, is diagnosed with chronic ischemic microvascular dz w/decreased cortical volume, resting pulse of 58, obese, low normal BP, free T4 1.3, and TSH 1.7. So my question is what merit does the TSH hold is treatment decisions now? Does ischemia to the CNS invalidate it? I would think that the hypothalamus and AP saved for the end?

she's Hash on replacement...TSH AND FT4 are normal...again NOT the thyroid...


and if the ischemia was somehow affecting the hypothalamus and/or the pituitary (which i'm assuming is what you are getting at) then TSH not the 1st to go...gonadotropins are the 1st (less necessary hormones go 1st life essential hormones last) to go so if ischemia was somehow causing an issue where her HPT axis is seemingly working (what with a NORMAL TSH and FT4) yet is having the nonspecific symptoms related to hypothyroidism, there would be issues with FSH/LH, E2/P4 and her periods...

TSH is the 1st and best test for determining thyroid function in someone on thyroid replacement.

 

[rokshana]

Sure. And all those labs occasional find pathology.

If you're going to send the TSH looking for thyroid problems based on clinical suspicion because of symptoms and not screening may as well send the T's

and that would be the difference between the internist's thought process and an endocrinologist's...

 

[jdh71]

and that would be the difference between the internist's thought process and an endocrinologist's...

Well I guess you can lecture the endocrinologists I trained with. The dogma I was taught was that if it's worth sending the TSH for a suspicion of thyroid issues, it's worth getting the T3 and T4 at the same time.

 

[TheSeanieB]

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[surge55]

Well I guess you can lecture the endocrinologists I trained with. The dogma I was taught was that if it's worth sending the TSH for a suspicion of thyroid issues, it's worth getting the T3 and T4 at the same time.

I read the guidelines for this specific issue. a normal TSH, especially as low as the one I got on my patient, means you don't get free t4/t3. in fact, they are not as good as TSH. TSH still is the gold standard.

now, if you have a patient with somewhat high TSH ie 2.5-4.1 depending on who you ask, then you get the free t4 and t3.

 

[rokshana]

Well I guess you can lecture the endocrinologists I trained with. The dogma I was taught was that if it's worth sending the TSH for a suspicion of thyroid issues, it's worth getting the T3 and T4 at the same time.

there is a difference between convenience and need...the OPs patient has KNOWN thyroid disease and on replacement, HAD a TSH drawn and it was NORMAL...at that point, there is no need for the FT4 and/or total T3...its not going to change your management...

if however the pt has no history of thyroid disease, there may be a place for the FT4/TT3 (as i did state in my previous posts).

the endocrinologist you trained with prolly realized it was easier to just not argue with dogmatic internists (but still shook their heads and rolled their eyes).

 

[rokshana]

Thanks. Your explanation makes sense. A little more information about the pt. She is post menopausal, has a normal stress test, ECG, and there are no signs of atherosclerosis. There are other signs of organ ischemia such as a BUN/creatinine of 25, eGFR of 83, mild pains consistent with ischemic bowel, memory problems, signs of dementia, and fatigue.

What would be the next step in her care? Thanks this is a confusing clinical situation for me.

what exactly are the symptoms that she is having that make you think they are thyroid related? i realize that she is on thyroid replacement so it is high on the differential, but thyroid symptoms are non specific so if your TSH is normal its less likely...but you may want to get more details about how she takes her thyroid med and if there have been any recent changes in how or where she gets her medications (taking it with new meds or changed pharmacies)..if new changes, then the changes may not reflect in the TSH (takes longer to see changes)...sound like you need to have endo at your hospital weigh in...

if you are seeing signs of ischemia is such varying places have you looked for a source for emboli?

 

[TheSeanieB]

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[rokshana]

So would it be appropriate to treat the pt I described by increasing the dose of levothyroxin by 12.5 mcg (from 75 to 87.5) due to the circumstances (average dose for hasimoto's is 125-150, pt has not been followed) and the severity of symptoms (bradycardia, chronic ischemic microvascular dz w/decreased cortical volume) and monitor the TSH? Or does the TSH of 1.7 exclude this treatment option?

you should talk to endocrine there before you increase her dose.

there is no average dosing for Hash...thyroid replacement is weight based so it will be different for different people.

 

[NotAProgDirector]

Either we are solving this medical student's homework, or we are giving them medical advice to treat a family member. Either way, SDN is really not the place.

 

[Darkskies]

it's funny you ask this; I had a patient with constipation, cold intolerance and depression. I thought for sure she had hypothyroidism, but her TSH is only 0.86. Given that it's so low, I won't even check a T4. she may just have all these symptoms separately and in medicine that is definitely possible. so I'll treat her constipation with stool softeners and treat her depression with an SSRI.

I'm just a lowly second year who hasn't been out on wards or had any clinical experience yet but why wouldn't you suspect that this could be a secondary hypothyroidism in this case if the TSH is low? Am I right in assuming that it's because the TSH level is within normal range(and not actually low) and because if it were a secondary hypothyroidism the patient might have symptoms of hypopituitarism as well?

EDIT: I realize SDN is not really the place for this and I apologize for continuing to discuss the topic but I really am curious to know so if someone would rather prefer to PM me instead of continuing this thread, that's fine as well!

 

[TheSeanieB]

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[Darkskies]

Student doctor network is a perfect place to learn and ask questions. Personal medical advice should not be given though.

To answer your question, secondary hypothyroidism would mean that there is pathology in the AP and that is why the thyroid is not producing and the pt is hypothyroid. In the case mentioned above, the pt has Hashimoto's where the thyroid is being damaged by the immune system.

This goes to my question. I am trying to understand the art of clinical reasoning thru a complex case where the standard algorithm may not apply and have not found anything on Medscape or Up To Date that has helped. This is homework but no assignment is due.

Thanks for the reply, TheSeanieB but my question was actually geared to the quote by surge55 and not your original clinical scenario. In surge55's post he was wondering if an undiagnosed patient might have some form of hypothyroidism due to symptoms but the TSH turned out to be .86 which he says is low and thus he ruled out hypothyroidism but I'm wondering why it couldn't be a low TSH due to a secondary hypothyroidism(AKA pituitary/hypothalamus issue).

 

[jdh71]

I read the guidelines for this specific issue. a normal TSH, especially as low as the one I got on my patient, means you don't get free t4/t3. in fact, they are not as good as TSH. TSH still is the gold standard.

now, if you have a patient with somewhat high TSH ie 2.5-4.1 depending on who you ask, then you get the free t4 and t3.

there is a difference between convenience and need...the OPs patient has KNOWN thyroid disease and on replacement, HAD a TSH drawn and it was NORMAL...at that point, there is no need for the FT4 and/or total T3...its not going to change your management...

if however the pt has no history of thyroid disease, there may be a place for the FT4/TT3 (as i did state in my previous posts).

the endocrinologist you trained with prolly realized it was easier to just not argue with dogmatic internists (but still shook their heads and rolled their eyes).

Ok guys. Whatever.

Saving lives and curing disease.

 

[Instatewaiter]

Thanks. Your explanation makes sense. A little more information about the pt. She is post menopausal, has a normal stress test, ECG, and there are no signs of atherosclerosis. There are other signs of organ ischemia such as a BUN/creatinine of 25, eGFR of 83, mild pains consistent with ischemic bowel, memory problems, signs of dementia, and fatigue.

What would be the next step in her care? Thanks this is a confusing clinical situation for me.

Treat the TIA.

Thank you for this interesting consult.

 

[TheSeanieB]

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