I was diagnosed with hypothyroidism after my son was born. I have been on Levothyroxine 50 micro grams since then. Today I got my latest serum TSH level results and it’s come back as normal. I am confused because after reading the advice on these pages I didn’t take my medication on the day of this latest test (in all previous results I had taken my medication as usual on the day of the blood test). Can someone help me interpret what’s going on?
Serum TSH levels: Date - Result - Ref Ranges
10/2021 - 3.25mlU/L (ref ranges 0.30-3.94mlU/L)
09/2020 - 2.62mlU/L (ref ranges 0.30-3.94mlU/L)
05/2019 - 3.17mlU/L (ref ranges 0.30-3.94mlU/L)
05/2018 - 1.97mlU/L (ref ranges 0.30-3.94mlU/L)
03/2017 - 4.6mIU/L (ref ranges 0.30-3.94mlU/L) and Free T4 Level - 10.1pmol/L (ref ranges 12.3-20.2 pmol/L) This is the only T4 measure I have the results for…
I have a call with my doctor next week - but don’t really know what to ask. If I have no Levothyroxine in my system and my results are normal - do I no longer have a thyroid problem??
Any advice would be hugely appreciated 😁 x
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Jules0001
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In my view, you should have had another test in April/May 2017! With a view to seeing how you were progressing and increasing your dose, if needed.
1.97 is almost certainly too high for someone taking thyroid hormone medicine. You should have had FT4 also tested.
Then they ignored a rise in TSH in 2019. That was wrong.
The drop in 2020 was pretty minimal - just having the blood drawn at a different time could have made the difference from 2018.
And now, still too high a TSH result. And no Free T4 test.
They appear to be treating the TSH range as if any result from 0.30 to 3.94 is fine. Which it isn't. Think of playing darts where every dart that hits the board scores as a bull. We expect most on thyroid hormone treatments to have a TSH around 1 or lower.
Levothyroxine increases the circulating T4 - peaking about two hours after swallowing the tablet. Then falls away slowly.
You just might find the article below (and the full paper which you can access) interesting and/or useful.
The normal range: it is not normal and it is not a range
1. Martin Brunel Whyte
2. Philip Kelly
Abstract
The NHS ‘Choose Wisely’ campaign places greater emphasis on the clinician-patient dialogue. Patients are often in receipt of their laboratory data and want to know whether they are normal. But what is meant by normal? Comparator data, to a measured value, are colloquially known as the ‘normal range’. It is often assumed that a result outside this limit signals disease and a result within health. However, this range is correctly termed the ‘reference interval’. The clinical risk from a measured value is continuous, not binary. The reference interval provides a point of reference against which to interpret an individual’s results—rather than defining normality itself. This article discusses the theory of normality—and describes that it is relative and situational. The concept of normality being not an absolute state influenced the development of the reference interval. We conclude with suggestions to optimise the use and interpretation of the reference interval, thereby facilitating greater patient understanding.
Thyroxine has a half life of around seven days. So, skipping one day's dose would have a small effect on your hormone status and the body is also able to adapt to short term changes. Your TSH results suggest you may be a bit undermedicated. However, you should go by how you feel. Also, there can be short term thyroid failure after giving birth 'post partum thyroiditis' so you may not even need levothyroxine now although your blood tests suggest you may do.
It's best not to take levothyroxine within four hours or so of having the blood taken as it can make the results a little less accurate. Leving up to 24 hours since the last tablet will have a small effect on the blood test, nothing to worry about. It depends on how you feel, if you feel fine I would try slowly coming off levothyroxine to see how you do (restart it if you feel bad). If you still feel 'hypo' I would ask for an increase in your dose.
100 mcg levothyroxine or a little more is closer to a normal dose. TSH inscreases exponentially as fT3 and fT4 fall. I don't know if you are into mathematics but what this means is that it would take a similar amout of hormone to reduce TSH from 3.0 to 1.5 as it would from 1.0 to 0.5. Doctors often make the mistake of assuming the response to levothyroxine dose is linear and that a TSH of e.g. 3.0 is OK as it is within the reference interval. Most patients feel better with a TSH of around 1.0 or lower but this is not a hard and fast rule. Let your doctor know how you are and ask for a dose increase.
Levothyroxine doses vary but most people with a failed thyroid ('primary hypothyroidism') are on about 100 - 175 mcg. There are other forms of hypothyroidism that tend not to be recognised that may require higher doses of levothyroxine or liothyronine (T3).
When the thyroid fails a dose of 1.6 mcg per kilogram weight gives a good idea of an approximate dose, something to work from provided there is flexibility in treatment.
A spreadsheet with several active formulas which work out possible levothyroxine requirements including NICE NG145 guidelines. These formulas are referred to in the document above.
This is an Excel spreadsheet but is likely to work in other spreadsheet software.
Only skimmed it but it looks very informative. All these studies only look at simple primary hypothyroidism (failed thyroid gland) and so should be seen as a rough starting point. Individual patients may vary considerably in their T3, T4 dosage requirements.
I find that people (patients and doctors) have a tendency to see a formula and treat it as gospel. We can work out areas of triangles using formulas due to Euclid, Pythagorus, et al. - so we can work out levothyroxine doses simply because there is a formula.
There are plenty of papers showing massively higher doses are needed by some - a classic being gastroparesis.
But the first stumbling block is most cannot demonstrate the patient is suffering simple primary hypothyroidism. It is quite hard to do if you only measure TSH with an occasional Free T4 if you are lucky.
50mcg is a starter dose, you should have had increases in your dose over the last 4 years. Your current TSH level is way too high for someone on thyroid hormone replacement. The aim of a treated Hypo patient on Levo only, generally, is for TSH to be 1 or below with FT4 and FT3 in the upper part of their reference ranges, if that is where you feel well.
How do you feel?
Just testing TSH is inadequate. We need at least FT4 as well, preferably FT3 too. The FT4 and FT3 are the thyroid hormones and testing these gives our hormone levels. TSH is a pituitary hormone, not a thyroid hormone, and although useful for diagnosis it's not a lot of use once we are taking thyroid hormone replacement.
If I have no Levothyroxine in my system and my results are normal - do I no longer have a thyroid problem??
If you think that by leaving 24 hours between last dose of Levo and blood draw means there is no Levo in your system, that is incorrect. You will have levothyroxine in your system.
Levo has a half life of 7 days so whatever you take today then half of that amount will still be in your system in 7 days time, along with what has been taken previously and built up.
The reason we suggest leaving 24 hours since last dose is to get as close to the normal amount of circulating hormone as possible. If you take your Levo before the test your result will show a spike in FT4 level as Levo peaks in the blood 2-4 hours after ingestion which gives a false high FT4 result, leaving longer than 24 hours gives us a false low result.
However, you do not have an FT4 result, you only have TSH so we don't know your actual thyroid hormone levels.
TSH level varies throughout the day, it's highest between midnight and 3am then lowers throughout the day, with a small rise around 9am, then the lowest point is about 1pm then a gradual rise. We always suggest testing no later than 9am to give the highest possible TSH - this then hopefully prevents a reduction in Levo dose or prompts an increase in dose, where necessary.
Maybe the difference in the TSH levels you have posted is because you may have had the tests done at different times rather then all being done early morning. Also coffee and certain foods may affect TSH level so it's best to have water only before the test to get the most accurate result.
Your current result should prompt your GP to raise your dose. If he doesn't then point out the following:
You are obviously undermedicated so no wonder you're not feeling great. High TSH = low FT4 and FT3. You need an increase in your dose of Levo. Use the information I've given you to get that increase and make sure FT4 at least is added to next test, preferably FT3 as well. Ask for vitamins to also be tested, if GP wont do all these tests then do them privately with one of our recommended labs, the answer will be in the results of full testing.
Leaving your levo off for 24 hours, or taking it on the day of the blood draw, will have no effect on your TSH because it doesn't move that fast. It would have an effect on your FT4, if they tested that - which they should - but not the TSH. So, your TSH is telling you that you are very under-medicated, but how do you feel? Do you still have symptoms?
Hi Greygoose, I feel terrible. I am exhausted! My mood is very low, I feel jittery and anxious, food has no taste or appeal. I have no libido and painful muscles - my arm muscles feel heavy and weak at the same time - does that make sense. ?! I will ask my doctor about getting the other tests done. Sounds like I may have been under medicated for some time…they have never suggested that my dose of Levo needs to increased…
The average doctor knows next to nothing about thyroid. They are usually way out of their depth when treating hypo patients. So, we the patients, have to try and keep them up to scratch. If you never ask for an increase, they will assume that you are on the right dose and their job is done - they're not going to raise the subject themselves if they feel on shaky ground. So, if we feel we need an increase, we have to ask for it - and insist on having it.
Part of the trouble is the so-called 'normal' blood test ranges. Doctors have trouble interpreting blood test results at the best of times, but tend to think that if something is 'in-range' it has to be good. Even it it's right at the top or right at the bottom of the range. If it's still inside those imaginary boundaries it has to be 'normal'. They do not understand how ranges are arrived at, nor about results still being too high or too low even within the range, nor that everybody is different and needs a different level to feel well. So, we have to keep reminding them.
But the TSH of a person with no thyroid problems (euthyroid) is around 1, never more than 2, and at 3 you are hypo. Even getting the TSH down to 1 in most hypos is not good enough, because a hypo person, taking exogenous hormone, tends to need more thyroid hormone to feel well than a euthyroid person whose thyroid is fully working. And the TSH - to a certain extent - only follows the level of the thyroid hormones. It does not lead them.
Hi if on Levo regularly especially for a number of years it can take 4-6 weeks for it to leave your system entirely. Missing one dose might make a miniscule difference. But it seems your TSH is much too high. You need your FT4 and FT3 levels tested as they are far more accurate than TSH alone.
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