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What affects the level of TSH: why it is important and how to properly prepare for the study

Often in laboratory studies, we note the deviation of any indicator (in a biochemical, clinical or hormonal blood test) from the range of reference values ​​​​(not to be confused with the concept of the norm). These deviations, as a rule, cause anxiety in patients, expectation of a difficult diagnosis, long-term medical or even surgical treatment. The doctor, seeing changes in the analysis, determines the tactics of management, observation, makes the right choice of therapy. Therefore, it is extremely important that the result of the analysis is as correct as possible.

To obtain objective results, it is necessary to properly prepare for a laboratory test: donate blood at a certain time of the day, first stop taking medications.

If at least one of the conditions is not met, then the probability of obtaining an incorrect, “untrue” result increases.

In some situations, the doctor may experience a number of difficulties associated with the interpretation of the tests. For example, the results may not correspond or contradict the clinical picture, the patient’s condition. Many diseases can occur with a varied combination of altered levels of TSH and thyroid hormones – T3, T4, which requires a different approach to treatment. As a result, a re-examination may be necessary.

The most common hormonal study in the world is a blood test for the level of thyroid-stimulating hormone (TSH). This hormone is necessary for the diagnosis of thyroid dysfunction, control of ongoing treatment, and pregnancy management.

When to take TSH:

If you have any of the following symptoms: persistent weakness, swelling, dry skin, decreased ability to work, muscle weakness, feeling of a lump in the throat, hair loss, mood swings, tearfulness, heart palpitations, shortness of breath, internal trembling, constipation or frequent stools, sweating , decreased memory, concentration, feeling of sand in the eyes.
Weight gain, weight loss without an obvious external cause.
Violation of the menstrual cycle.
Planning for pregnancy and pregnancy.
Presence of type 1 diabetes.
Relatives with autoimmune diseases: endocrine system, vitiligo, alopecia, pernicious anemia, rheumatological pathology.
Operations and radiation in the neck.
Heart rhythm disturbances, heart failure (shortness of breath, edema).
Mental illness, dementia, muscle damage.
Increased cholesterol levels, changes in the lipid profile, progressive atherosclerosis (the formation of fatty plaques in the vessels), lipomas.
Medications: levothyroxine, tyrosol, lithium (rare), amiodarone/cordarone, or pre-medication screening (amiodarone/cordarone).
What affects the analysis of TSH:
Time of day: TSH concentration decreases by 20–60% of baseline during the day.


• iodine preparations, dietary supplements with algae, amiodarone / cordarone – a decrease (more often) and an increase in TSH;

• steroid hormones (prednisolone, dexamethasone) – decrease in TSH;

• immunomodulators (interferon-alpha) – increase in TSH, biological therapy in rheumatology – decrease in TSH;

• biotin – decrease in TSH;

• beta-blockers – possible increase in TSH.

Physiological state: 30% of women experience a decrease in TSH levels in the first half of pregnancy. At the same time, total T3 and T4 can be 15% higher. In the 3rd trimester, on the contrary, an increase in TSH is observed.
Viral infections, including COVID-19 – decrease in TSH.
Violation of the water and electrolyte balance, kidney pathology, dehydration – increase / decrease in TSH.
Stress, sleep disturbance – decrease in TSH.

How to donate blood for TSH level:

Donate blood strictly on an empty stomach – from 8.00 to 9.00. In the morning you can drink a small amount of clean water.
Levothyroxine preparation (euthyrox, l-thyroxine) should not be taken before blood sampling.
Discuss the list of medications you take with your doctor in advance. Do not forget to report all the drugs and dietary supplements you take, even those prescribed by another specialist: a general practitioner, cardiologist, rheumatologist, ENT, infectious disease specialist, dermatologist.
Try to eliminate physical and psycho-emotional stress for 24 hours.
Do not smoke for 3 hours prior to blood sampling.
Do not donate blood for TSH during SARS, menstruation.
Follow-up follow-up 4-6 weeks after the initial determination (or at another time recommended by your doctor if you are already receiving treatment for thyroid disease).

If you have any questions about preparing for the study, be sure to ask your doctor. This may apply to any research, not only laboratory and not only in the endocrinologist’s office. The doctor will always answer your questions and give the necessary explanations.

In the following publications, we will discuss the concept of reference value and norm, which affects the levels of other hormones, how to properly submit material for analysis, the features of the course of thyroid diseases, diabetes mellitus, and their combination with other pathologies.