TSH: Normal Values, a Raised and a Lowered Result
TSH is the one number that decides whether you go any further. It does not measure thyroid hormones but the message the pituitary sends to the gland: when the gland works too weakly the message gets louder and TSH rises, and when it works too hard the message quietens and TSH falls. That is why TSH is the first test for fatigue, gaining or losing weight, hair loss, an irregular cycle and palpitations. This article explains the normal values, what a raised and what a lowered result mean, when fT4, fT3 and antibodies are done and when a result should be repeated before any conclusion is drawn.
Normal TSH values
| Test | Usual reference range | What it shows |
|---|---|---|
| TSH | 0.4 to 4.0 mIU/L | How hard the pituitary is “pushing” the thyroid |
| fT4 (free thyroxine) | 9 to 19 pmol/L | The gland's main hormone, the body's reserve |
| fT3 (free triiodothyronine) | 2.6 to 5.7 pmol/L | The active form, working in the tissues |
A raised TSH: the gland is working too weakly
A high TSH means the pituitary is strengthening the message because it is not getting enough hormone from the gland. How serious that is only becomes clear from the fT4 beside it.
| TSH | fT4 | How it is read |
|---|---|---|
| Raised | Normal | Subclinical hypothyroidism: the gland is still holding on, but with effort |
| Raised | Lowered | Clear hypothyroidism |
| Mildly raised once | Normal | Often temporary; the test is repeated in 6 to 12 weeks |
The symptoms that go with reduced function are fatigue that sleep does not shift, feeling cold, dry skin, hair loss, constipation, a slower pulse, a puffy face in the morning and weight gain with no change in diet. None of them on its own is proof, because they all occur for other reasons too.
A lowered TSH: the gland is working too hard
A low TSH with a raised fT4 or fT3 points to hyperthyroidism. It comes with palpitations, tremor, sweating, insomnia, weight loss with a normal appetite, diarrhea and a feeling of restlessness. A low TSH with normal hormones is subclinical hyperthyroidism and calls for monitoring, because over time it affects the heart rhythm and the bones.
TSH can also be low without any disease of the gland: in the first trimester of pregnancy, in severe illness unrelated to the thyroid, with corticosteroids and with some medicines. That is why a result is always read together with the person, not on its own.
When antibodies are tested
Antibodies answer the question why, not how much. They are done when TSH and the hormones have shown that something is wrong, not as a routine addition to every result.
- anti-TPO and anti-Tg: raised in Hashimoto's thyroiditis, the most common reason for reduced function.
- TRAb: raised in Graves' disease, the most common reason for increased function.
- Ultrasound of the thyroid: it looks at the structure and at nodules, but says nothing about function. A finding of a “nodule” and a finding of a “raised TSH” are two different questions.
TSH in pregnancy and when planning one
In pregnancy TSH is not read against the general range. The need for hormone rises in the very first weeks, and the cut-offs are lower and differ by trimester, so the ranges the laboratory provides for pregnant women are used. A woman already on treatment should report a pregnancy immediately, because the dose is as a rule adjusted early. When planning a pregnancy and after repeated losses, TSH is part of the basic panel.
When a result should be repeated
TSH varies through the day and is highest in the early morning, so blood is drawn in the morning and always at roughly the same time of day when it is being compared with a previous result. Biotin from hair and nail supplements can shift the result on the analyzer, so it is stopped two days before the blood draw. After an infection or during a more serious illness the test is postponed. One borderline result is not a diagnosis; it is repeated in 6 to 12 weeks, together with fT4.
What an endocrinology appointment looks like
Bring the result with its printed reference range, a list of your medicines and supplements and any earlier results. The endocrinologist examines your neck, reads the TSH together with fT4 and, if needed, with antibodies and an ultrasound, and then says whether this is a condition to be monitored or a condition to be treated, and when the next check is. No referral is needed for an appointment with us.
Prices
| Service | Price |
|---|---|
| Endocrinology appointment (Dr Zorana Đuran) | 7.000 RSD |
| Endocrinology appointment + ultrasound of the thyroid (Dr Zorana Đuran) | 12.000 RSD |
| Endocrinology appointment + ultrasound of the thyroid (Dr Nemanja Nenezić) | 14.000 RSD |
| Internal medicine appointment (Dr Andreja Kovačević) | 6.000 RSD |
Check it now
- Thyroid report interpreter: enter TSH, FT4, FT3 and anti-TPO and see what the combination means.
Frequently asked questions
What are normal TSH values?
Most often 0.4 to 4.0 mIU/L, but the range depends on the laboratory and you always read the one printed beside your own result. In pregnancy separate, lower ranges apply by trimester.
Does TSH have to be taken fasting?
Fasting is not required, but blood is drawn in the morning, because TSH is highest in the early hours and that makes it comparable with the previous result. If glucose and lipids are being drawn at the same time, their preparation rules apply.
What does a raised TSH with a normal fT4 mean?
That is subclinical hypothyroidism: the gland is still keeping the hormones up, but with a stronger message from the pituitary. Whether to treat depends on how high the TSH is, on symptoms, on antibodies and on plans for pregnancy, not on one number.
Can supplements spoil the result?
Biotin in larger doses, common in hair and nail preparations, interferes with the method TSH is measured by and can give a falsely low or a falsely high result. It is stopped two days before the blood draw and mentioned to the doctor.
Is a thyroid nodule the same thing as a bad TSH?
It is not. The ultrasound sees structure, TSH measures function. A nodule can be there with a perfectly normal TSH, and the function can be disturbed without a single nodule. That is why the two findings are interpreted together.
Book an appointment
If your TSH is outside the range, or your symptoms persist despite a normal result, book an endocrinology appointment at the Miren Medic clinic. The test, the ultrasound and the interpretation come from one place, without a referral, with a clear date for the next check.
