Thyrotropin (S-TSH), a hormone regulating the functions of the thyroid. The test is performed when a thyroid disorder is suspected.
When should TSH be measured?
Fatigue, low mood, constipation, weight gain, feeling cold, decreased memory function and a slow pulse may be signs of an underactive thyroid (hypothyroidism, Greek hypo for ‘under’ or ‘below’). The skin may be dry, rough, cold or pale and the hair may turn rough or fall out. The symptoms may also be vague.
Sweating, fatigue, irritability, muscle weakness, heart palpitations, weight loss, overactive bowel movements and thirst may be signs of an overactive thyroid (hyperthyroidism, Greek hyper for ‘over’ or ‘above’). Women may experience disturbances of the menstrual cycle.
What does the test measure?
The test is used to examine whether the thyroid is functioning normally. TSH stands for thyroid stimulating hormone. TSH is indirectly essential in the production of thyroid hormones, in other words thyroxine and triiodothyronine, via the body’s regulatory mechanism.
A deficient amount of thyroid hormones increases the amount of TSH in the blood. The pituitary gland increases the production of TSH to activate the thyroid to produce more thyroid hormones.
If the thyroid is overactive, the TSH levels are reduced. Excessive thyroid hormones in the bloodstream reduce or even prevent the secretion of TSH in the pituitary gland.
How to interpret the result?
Normally, the result is:
Adults: 0,5-3,6 mU/l
The results indicate whether the levels of thyroid hormones in the body are too high or too low. However, the test does not give the reason for a result falling outside the reference range. An abnormal TSH result only means that additional tests are in order.
Additional tests usually help diagnose a possible thyroid disease. All tests can be completed before having a doctor’s appointment so that the results are available for the diagnosis. Other tests are not usually needed. If abnormal values are observed in the tests, you should consult a physician.
Read more about defining reference values.
What can cause elevated TSH values?
- The most typical reason for elevated TSH values is a disruption in the functions of the thyroid.
- Chronic hypothyroidism is the second most common diagnosis after inflammation of the thyroid (autoimmune thyroiditis). Other possible reasons may be recent thyroidectomy and radioiodine therapy.
- Temporary reasons for hypothyroidism include subacute thyroiditis and side effects of some medicinal products.
- Other, rare reasons for elevated TSH levels include a tumour in the pituitary gland and medicinal products.
What can cause decreased TSH values?
- Low TSH values are usually caused by primary hyperthyroidism (overactive thyroid). In hyperthyroidism, the TSH levels often drop to below 0.02 mU/l.
- In hypothyroidism resulting from a disruption of the central nervous system (pituitary gland or hypothalamus), the TSH values fall within or below the reference values.
- Low TSH values also occur in subclinical hyperthyroidism, nodular thyroid disease, early stages of thyroiditis and after administering thyroxine medication.
Other illnesses may also result in TSH levels falling outside reference values. Severe chronic diseases and some types of medicinal products, for example, can cause abnormal TSH values.
Typical further examinations after an abnormal TSH test result include:
- Free thyroxine or thyroid hormone (T4V). The test measures the amount of free thyroxine in the blood.
- Thyroid peroxidase antibodies (S-TPOAb). Elevated TPO antibodies are a sign of an autoimmune thyroid disease.
- TSH receptor antibodies (TSHRAb). These become attached to the thyroid cells, either accelerating or preventing the production of thyroid hormones.
SYNLAB test list: Thyrotropin (2832 S -TSH) https://www.yml.fi/tuotekuvaus_show.php?tuotenro=373
Terveyskirjasto health library: Thyrotropin (P-TSH)
Fasting is not required
This examination does not require fasting