TSH too high or below normal? What thyroid tests should be done? 

Abnormal TSH (thyroid-stimulating hormone) levels can be the first sign that something is wrong with your thyroid. Both excessively high and low TSH levels can indicate a thyroid disorder. In this article, we explain what an abnormal TSH level means and which thyroid tests should be performed to make an accurate diagnosis.

TSH hormone too high – what does it mean?

An elevated TSH level usually suggests that the thyroid gland is working too slowly, meaning hypothyroidism . This may be caused by factors such as:

• Hashimoto's disease (autoimmune thyroiditis),
• iodine deficiency,
• side effect of some medications,
• condition after radioactive iodine treatment or thyroid surgery.

Symptoms of hypothyroidism:

• chronic fatigue,
• weight gain,
• feeling cold,
• dry skin and hair loss,
• slow heart rate,
• low mood or depression,
• menstrual disorders.

TSH too low – what does it mean?

A low TSH level may indicate hyperthyroidism —a condition in which the thyroid gland produces too much hormone. This may be the result of:

• Graves' disease (autoimmune hyperthyroidism),
• autonomic nodules,
• thyroiditis (e.g. subacute),
• overdose of thyroid hormones in the treatment of hypothyroidism.

Symptoms of hyperthyroidism:

• feeling of anxiety, irritability,
• heart palpitations,
• weight loss despite good appetite,
• excessive sweating,
• shaking hands,
• insomnia,
• menstrual cycle disorders.

What thyroid tests are worth doing?

The TSH level is just a starting point. To assess the full picture of thyroid function, it's worth performing:

1.   FT3 and FT4 hormone concentration tests

Free thyroid hormone fractions (FT3 and FT4) reflect the amount of biologically active hormone available in the bloodstream.

• FT4 – its level is usually elevated in hyperthyroidism and decreased in hypothyroidism .
• FT3 – is a more sensitive indicator when hyperthyroidism , especially in its early stages or in the case of so-called conversion hyperthyroidism.

2.   Thyroid antibodies:

• aTPO (anti-TPO) – the result is elevated in Hashimoto’s disease and Graves’ disease.
• aTG (anti-TG) – elevated results also occur in autoimmune diseases.
• TRAb – is a test that checks the presence of antibodies against thyroid-stimulating hormone (TSH) receptors in the body, characteristic of Graves’ disease (hyperthyroidism) but also of Hashimoto’s disease.

3. Thyroid ultrasound

Imaging examination showing size, structure, and any focal lesions (e.g., nodules). May indicate inflammation, hyperplasia, or other pathologies.

4.   Thyroid scintigraphy (if recommended by your doctor)

Radioisotope test – allows to determine the metabolic activity of the nodule (so-called “cold” or “hot” nodule).

When should you see an endocrinologist?

It is worth seeing a specialist when:

• TSH level is outside the norm (high or low),
• you have symptoms suggesting thyroid disorders,
• there are autoimmune diseases in the family,
• you are planning a pregnancy or are pregnant (thyroid hormones are crucial for fetal development),
• you are undergoing hormonal treatment and need monitoring.

The importance of TSH in pregnancy – why is it worth monitoring?

TSH is one of the most important indicators of thyroid function, including during pregnancy. Maintaining a healthy TSH level in pregnant women is crucial for the mother's health and the proper development of the baby's brain and nervous system. TSH levels during pregnancy differ from those outside of pregnancy – they are usually lower, especially in the first trimester, due to the influence of the β-hCG hormone on the thyroid gland. Both excessively high and too low TSH levels can increase the risk of complications, such as miscarriage, premature birth, or fetal developmental disorders. Therefore, TSH testing is a routine part of pregnancy testing and should be regularly monitored, especially in women with thyroid disease or a personal or family history of thyroid disease.

Abnormal TSH levels don't always indicate disease, but they should never be ignored. It's crucial to expand your diagnostic workup to include FT3, FT4, thyroid antibodies, and thyroid ultrasound. This allows for early detection and effective treatment of thyroid disorders before they cause more serious health problems.

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