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Originally published on 12th February 2016 Last updated on 11th February 2019
TSH is often regarded as an inaccurate way to measure thyroid function in the thyroid community.
What is TSH?
TSH stands for ‘Thyroid Stimulating Hormone’ and is a hormone secreted by the pituitary gland. It serves as an average read out over the previous four to six weeks of your thyroid levels.
TSH is a pituitary hormone that sends a signal to the thyroid gland. It is produced by the pituitary gland.
It goes like this:
Hypothalamus -(sends signal to)-> Pituitary -(sends signal to)->Thyroid.
With a healthy thyroid, the pituitary gland knocks on the thyroid’s door, signalling it to work and produce so much of certain hormones. It does this by releasing TSH. The thyroid answers the door and does what it’s told by the pituitary by releasing the correct amount of thyroid hormone. Therefore, the pituitary gland isn’t having to knock too much, which equals a low TSH. This is good.
TSH in Hypothyroidism
In a person with an underactive thyroid (hypothyroidism) and not medicated, the pituitary gland knocks on the door of the thyroid gland, trying to give orders, but the thyroid ignores it. It doesn’t respond. The pituitary bangs harder and louder and more often on the door, as the thyroid continues to ignore it, and doesn’t produce the hormones it should be. This equals a high TSH. This isn’t good.
Bringing TSH Down
Theoretically, if you put the hormones your body is lacking and thyroid is failing to produce, in to your body, the TSH will come down, as the pituitary doesn’t need to knock on the door so much, as it can see that the body is getting the hormones it needs. So doctors generally see the TSH being low as your body having what it needs.
However, this isn’t always the case.
Having a ‘normal’ TSH is one thing, however, your body actually performing properly is another. TSH is a pituitary hormone, not a thyroid hormone. It does not tell you your actual thyroid hormone levels, it does however give an indication of them. Free T3 and Free T4 need testing to check actual thyroid hormone levels and the full thyroid panel should always be used to to get the most comprehensive view of your thyroid health.
‘Normal’ TSH Levels
An analogy you could use when your doctor tells you that your TSH is fine, but you don’t feel ‘fine’ could be;
Would you be happy with a heating engineer telling you your central heating is working fine, just because the thermostat reading is normal, when the radiators are cold and the house is freezing?
As this study states: “Screening exclusively with TSH will result in misdiagnosis of some cases, whilst other conditions may be missed altogether (by virtue of returning a TSH result that falls within the reference range despite overt hypothalamic–pituitary–thyroid dysfunction).” 
You can still feel unwell with a ‘normal’ TSH level because:
- Your body could be failing to convert the T4 (thyroxine, also known as Levothyroxine and Synthroid) to T3, which makes you feel unwell, still.
- Your Free T3 and T4 levels could be below optimal or at the bottom of the range. TSH doesn’t tell us this.
- You TSH may be ‘in range’ but not optimal.
- You could have adrenal gland dysfunction (high or low cortisol levels) or low iron levels, meaning the T3 isn’t being carried to all the places it needs to.
The next time your TSH is ‘normal’ and you still feel unwell, one of the above reasons could well be why. Many thyroid patients find that whilst their TSH is OK, their Free T3 and Free T4, or even Reverse T3 isn’t optimal and so they still feel unwell. You should always be working to optimise your levels.
(see here why testing Reverse T3 is often controversial and why I’m dubious about whether it’s truly useful. I lean more towards ‘no’, however, you will see other thyroid resources suggesting we must have it checked.)
If your doctor won’t test a full thyroid panel, you may explore ordering your own from online lab services.
Medichecks is a popular place in the UK, where you can order the all important thyroid function test, and thyroid antibodies to check for autoimmune hypothyroidism (Hashimoto’s).
LetsGetChecked cover most countries, and offer the thyroid function test, Hashimoto’s testing and many more, all from the comfort of your own home.
Now you know all of this, please don’t stay undiagnosed, under-medicated or be dismissed due to just having TSH tested. Obtain a copy of your test results and have a look for yourself. Ensure you’re having the full thyroid panel tested to get the most comprehensive view of your thyroid health.
TSH gives an indication of what’s going on, but not the full picture.
Did you know that TSH alone isn’t accurate? Share your thoughts in the comments section below.
You can click on the hyperlinks in the above post to learn more and see references to information given.
The book Be Your Own Thyroid Advocate: When You’re Sick and Tired of Being Sick and Tired, which builds on this article in detail and tells you everything you need to know to become an active participant in your own thyroid health and understand what you can do to get better.
Glenda DredgeApril 6, 2023 at 12:31 am
Hi, just joined this support group. I was diagnosed 12 months ago with an underactive thyroid and commenced on levothyroxine, it has taken me this long to get the GP to increase my dose. I have had to fight all the way, I was informed by the receptionist that my results were normal but I still felt so very unwell, I got a printout of my results and discovered that my TSH was still above range so requested to speak to a doctor. He reluctantly increased my dose from 50mcg to 75mcg.
Still feeling rubbish after 12 weeks I increased my dose to 100mcg and told the GP I had done this, I was asked to make an appointment ( which I had been trying to do but not getting anywhere). I saw a practice nurse who suggested I double my HRT dose as I still felt awful, this just gave me migraines everyday, so went back to usual dose. After much persuasion I finally got my levo increased to 125mcg, I cited the N.I.C.E. Guidelines to them which state they should take the patient’s symptoms into account when treating. I feel better than I did but far from well, some symptoms have improved but others are no different. I’m not as tired but then I’m only working on an as and when basis now, I took early retirement believing my symptoms were caused by stress at work. I am a registered nurse of over 40 years.
I truly believe I have been symptomatic for many years, I’ve had endoscopy for gastric pain and reflux, mainly resolved now even though my gastric tablets have been halved. I’ve seen physiotherapists because of joint pains. I’ve tried inhalers as I get really short of breath with minimal exercise. I’ve had a persistent irritating cough for many years, which I have complained about several times, I got a chest X-ray and told it was normal, they have done nothing since.
I still get very tired and have aches and pains everywhere but the hardest part is trying to explain to my husband and sons that I’m not lazy, I’m just exhausted all the time. Why I’m depressed.
I have eventually got another appointment with the GP surgery but again it’s with a nurse practitioner who will be unable to make any alterations to my dose of levo.
P.s. I got my T3 and T4 done privately and my levels are midway in the normal range, my TSH is in the lower end of the normal range. I just want to feel well, be able to keep the house tidy, play with my 6 year old grandson, climb steps, hills etc without having to stop and get my breath back, lose the excess weight, go to the gym with my husband. WHY DO WE HAVE TO FIGHT FOR OUR TREATMENT. I want to be able to enjoy my retirement and do things with my family. Sex would be nice occasionally!
Mike SharpNovember 3, 2022 at 9:22 am
Had been balanced on 200mcg Levothyroxine for 10 years. Changed doctor who looked at low TSH and high T4, and decided I was overdosed. She was obsessed by risk of heart and bone problems, so reduced Levothyroxine by 25mcg. This was despite no signs of hyperthyroidism – resting heartbeat was 55bpm and blood pressure 120/80. Went obvious hypothyroidal after 2 months. This was only resolved by persuading doctor to return to 200mcg. Would this class as malpractice?
Have since had a full panel done in Bulgaria. Two Bulgarian endocrinologists also decided results showed overdosing, and ignored FT3 being mid-range. Recommended reducing Levothyroxine by 50mcg, despite evidence from previous 25mcg reduction. Are these medics mad, or am I? How many patients’ lives are they ruining?
C RingMarch 10, 2022 at 7:35 pm
Very new to all this and have found your site informative and have ordered the book. Looking back I’ve been ill for over 20 years but only now because of high TSH have I been put on Levo. The complexity and variations are mind boggling to a newbie. Latterly I’ve been treated for arthritic flare up and muscle pain, IBS and reflux. All contributed to thyroid problems. Asked doctor for blood work out of desperation and have now got a diagnosis that makes sense. Looking forward to feeling better and now I have info that supports my foggy brain and can move forward.
Linda BazukApril 7, 2021 at 2:06 pm
H i Rachel, I just love the information you have offered. I am from Winnipeg, Canada. Have you ever heard of Jodi Knapp? She is American and offers a plan to completely eliminate Hypothyroidism. It costs only $49.00 and I am thinking about going for it. Do you have any comments or opinions about it? Please reply, I think you are such a good mentor. Best regards, Linda Bazuk.
Rachel HillApril 11, 2021 at 9:32 am
Hi Linda, I haven’t heard of this before but would be very cautious.
EloiseApril 7, 2019 at 7:58 pm
Thanks for the terrific post