- Reference values
- What can the results mean
- High TSH
- Low TSH
- How the TSH exam is done
- What is ultra sensitive TSH
- When the TSH exam is requested
The TSH exam serves to assess thyroid function and is usually requested by the general practitioner or endocrinologist, to assess whether this gland is functioning properly, and in case of hypothyroidism, hyperthyroidism, or in the case of differentiated thyroid cancer, such as follicular or papillary, for example.
Thyostimulating hormone (TSH) is produced by the pituitary gland and its purpose is to stimulate the thyroid to produce hormones T3 and T4. When TSH values are increased in the blood, it means that the concentration of T3 and T4 in the blood is low. When it is in low concentrations, T3 and T4 are present in high concentrations in the blood. See what are the essential tests to evaluate the thyroid.
Reference values
TSH reference values vary according to the person's age and the laboratory where the test is performed, and are usually:
| Age | Values |
| 1st week of life | 15 (μUI / mL) |
| 2nd week up to 11 months | 0.8 - 6.3 (μUI / mL) |
| 1 to 6 years | 0.9 - 6.5 (μUI / mL) |
| 7 to 17 years | 0.3 - 4.2 (μUI / mL) |
| + 18 years | 0.3 - 4.0 (μUI / mL) |
| In pregnancy | |
| 1st quarter | 0.1 - 3.6 mUI / L (μUI / mL) |
| 2nd quarter | 0.4 - 4.3 mUI / L (μUI / mL) |
| 3rd quarter | 0.4 - 4.3 mUI / L (μUI / mL) |
What can the results mean
High TSH
- Hypothyroidism: Most of the time, high TSH indicates that the thyroid is not producing enough hormone, and therefore the pituitary gland tries to compensate for this by increasing TSH levels in the blood so that the thyroid performs its function properly. One of the characteristics of hypothyroidism is high TSH and low T4, and may indicate subclinical hypothyroidism when TSH is high, but T4 is within the normal range. Find out what T4 is. Remedies: The use of low doses of drugs against hypothyroidism or other remedies, such as Propranolol, Furosemide, Lithium and medicines with iodine, can increase the concentration of TSH in the blood. Pituitary tumor can also cause an increase in TSH.
Symptoms related to high TSH are typical of hypothyroidism, such as tiredness, weight gain, constipation, feeling cold, increased facial hair, difficulty concentrating, dry skin, fragile and brittle hair and nails. Learn more about hypothyroidism.
Low TSH
- Hyperthyroidism: Low TSH usually indicates that the thyroid is producing T3 and T4 excessively, increasing these values, and therefore the pituitary decreases the release of TSH to try to regulate thyroid function. Understand what T3 is. Use of medication: When the dose of the hypothyroid drug is too high, TSH values are below ideal. Other remedies that can cause low TSH are: AAS, corticosteroids, dopaminergic agonists, fenclofenac, heparin, metformin, nifedipine or pyridoxine, for example. Pituitary tumor can also lead to low TSH.
Symptoms related to low TSH are typical of hyperthyroidism, such as agitation, heart palpitation, insomnia, weight loss, nervousness, tremors and decreased muscle mass. In this case, it is normal for TSH to be low and T4 to be high, but if T4 is still between 01 and 04 μUI / mL, this may indicate subclinical hyperthyroidism. Low TSH and low T4, may indicate anorexia nervosa, for example, but in any case the diagnosis is made by the doctor who ordered the test. Learn more about treating hyperthyroidism.
How the TSH exam is done
The TSH test is done from a small blood sample, which must be collected fasting for at least 4 hours. The collected blood is sent to the laboratory for analysis.
The best time to do this test is in the morning, as the concentration of TSH in the blood varies throughout the day. Before performing the exam it is important to indicate the use of some medication, especially thyroid remedies, such as Levothyroxine, as it can interfere with the exam result.
What is ultra sensitive TSH
The ultra sensitive TSH test is a more advanced diagnostic method that can detect minimal amounts of TSH in the blood that the normal test would not be able to identify. The diagnostic method used in the laboratories is very sensitive and specific, and the ultra sensitive TSH test is normally used in the routine.
When the TSH exam is requested
TSH testing can be ordered in healthy people, only to assess thyroid function, and also in case of hyperthyroidism, hypothyroidism, Hashimoto's thyroiditis, thyroid enlargement, presence of benign or malignant thyroid nodule, during pregnancy, and also to monitor the dosage of thyroid replacement drugs, in case of removal of this gland.
Usually, this test is requested for all people over 40 years of age, even if there are no cases of thyroid disease in the family.
