My thyroid test is normal but I still have symptoms. Why?

You feel tired all the time, the weighing scale keeps going up, or your hair is falling, so you get your thyroid checked. The report comes back normal. It is natural to wonder if the test missed something. In most cases, it did not. A normal TSH together with a normal FT4 is a reliable sign that your thyroid is working properly. The more useful question is: what else could be causing how you feel? You can check the pattern of your result with the thyroid report reader.

How reliable is a normal thyroid test?

Very reliable, as long as both TSH and FT4 are normal. TSH is extremely sensitive. Even a small fall in thyroid hormone makes the pituitary push TSH up, often before you notice any change. So if TSH is normal, an underactive thyroid is very unlikely.

For a full explanation of the numbers on your report, read the thyroid function test explained.

Can I have hypothyroidism with a normal TSH?

Rarely, yes, but only in one specific situation. If the pituitary gland itself is not working well, it may not send out enough TSH. Then TSH can look normal or low even though the thyroid hormone (FT4) is low. This is called central hypothyroidism. It is uncommon and usually comes with other clues, such as headaches, vision problems, missed periods, low sex drive or a past head injury or brain surgery.

This is why many doctors check FT4 along with TSH. If FT4 is low with a normal TSH, see an endocrinologist. Read more in unusual thyroid test results.

Testing only “T3, T4 and TSH” as totals can sometimes give confusing results, for example in pregnancy or on the contraceptive pill. Your doctor may ask for free T4 instead.

What else causes tiredness, weight gain and hair fall?

These symptoms are very common and are often blamed on the thyroid. In India, some of the most frequent real causes are:

• Iron deficiency and anaemia, especially in women with heavy periods and in vegetarians. Ferritin can be low even when haemoglobin is normal.
• Vitamin B12 deficiency, common in vegetarians and in people taking metformin for a long time. It causes tiredness, tingling and poor memory.
• Vitamin D deficiency, which can cause body aches and fatigue.
• Poor sleep and sleep apnoea. Loud snoring, waking up unrefreshed and daytime sleepiness, often with weight gain.
• Diabetes or prediabetes, which can cause tiredness and frequent urination. An HbA1c test helps. You can turn an HbA1c into an average sugar using the HbA1c to average glucose tool.
• PCOS in women, with irregular periods, acne, facial hair and weight gain.
• Depression and anxiety, which commonly cause fatigue, sleep changes and weight change.
• Weight gain from lifestyle, which is the most common reason of all: less activity, more refined carbohydrates and late meals.
• Medicines, such as some antidepressants, steroids, insulin and some diabetes and epilepsy medicines.

Hair fall in particular has many causes. Read hair loss and the thyroid. For weight, read can thyroid problems cause weight gain.

I am already on thyroid tablets and my TSH is normal. Why do I still feel tired?

Some people on levothyroxine still feel unwell even with a normal TSH. Before thinking about changing the thyroid treatment, doctors usually check:

• whether the tablet is being absorbed well, as tea, coffee, calcium and iron can interfere. Read how to take levothyroxine the right way.
• other causes from the list above, such as anaemia, B12, vitamin D, sleep and mood
• other autoimmune conditions that travel with Hashimoto’s, such as coeliac disease, vitamin B12 deficiency (pernicious anaemia) or, rarely, adrenal problems

Adding T3 tablets helps only a small group of people. Read liothyronine (T3) tablets.

Should I keep repeating the thyroid test?

Usually not. If TSH and FT4 are normal and you have no neck swelling or new symptoms, repeating the test every few months rarely adds anything. Exceptions include pregnancy, a strong family history, positive anti-TPO antibodies, or treatment with medicines that affect the thyroid. Your doctor will tell you when the next test is useful.

What should you ask your doctor?

• Is my FT4 also normal, not just my TSH?
• Should we check iron, ferritin, vitamin B12, vitamin D, HbA1c and blood count?
• Could my sleep, mood or medicines explain this?
• Do I need any hormone tests beyond the thyroid?

An endocrinologist can help when symptoms persist and the reason is not clear. See who an endocrinologist is or book a consultation.