How to read the result
The reference values for TSH in most laboratories fall within the range of approximately 0.4–4.0 mU/l, but the limits may differ slightly, so they are guided by the norms of a specific form. If TSH is elevated, but free T4 remains normal, we are talking about subclinical hypothyroidism - the most common option. If TSH is elevated and T4 is decreased, this is clear hypothyroidism. Low TSH with normal T4 and T3 is subclinical thyrotoxicosis, and low TSH with high hormones is overt thyrotoxicosis. Therefore, isolated TSH is almost always supplemented with free T4.
- TSH is high, T4 is normal - subclinical hypothyroidism
- TSH is high, T4 is low - obvious hypothyroidism
- TSH is low, hormones are normal - subclinical thyrotoxicosis
- TSH is low, T4 and T3 are high - obvious thyrotoxicosis
- Norms vary between pregnant women and trimesters
Why does TSH rise?
The most common cause is autoimmune thyroiditis, in which the immune system gradually damages the gland tissue, and it ceases to cope with the production of hormones. Less commonly, hypothyroidism develops after surgery on the thyroid gland, treatment with radioactive iodine, with severe iodine deficiency, and also as a side effect of a number of drugs. A temporary increase in TSH occurs in the recovery phase after serious illnesses and in subacute thyroiditis. Symptoms increase slowly: fatigue, chilliness, dry skin, constipation, weight gain, swelling, decreased memory and mood.
- Autoimmune thyroiditis
- Condition after surgery or treatment with radioactive iodine
- Severe iodine deficiency
- Taking certain medications
- Recovery after a serious illness
- Subacute thyroiditis in a certain phase
Why does TSH decrease?
Low TSH means too much thyroid hormone. Most often, this is due to Graves' disease - an autoimmune disease in which the gland works uncontrollably, or a node that produces hormones on its own. Another reason is thyroiditis, when inflamed tissue releases stored hormones into the blood. A decrease in TSH also occurs with an overdose of thyroid hormones. Characteristic signs: weight loss with a good appetite, palpitations, trembling hands, sweating, irritability, sleep disturbances, and in some people, changes in the eyes.
- Graves' disease (diffuse toxic goiter)
- Functioning thyroid nodule
- Thyroiditis with hormone release
- Excessive dose of replacement therapy
- The first trimester of pregnancy as a normal option
What to do after a deviation in the analysis
The first rule is not to start treatment based on one result. The analysis is repeated after a few weeks along with free T4, and if thyrotoxicosis is suspected, with free T3. Antibodies to thyroid peroxidase help determine whether there is an autoimmune process. Ultrasound shows the structure of the gland and nodes, and in case of suspicious nodes, a puncture is performed under ultrasound guidance. Blood is donated in the morning, separately from taking thyroid hormone medications. It is important to tell your doctor about your pregnancy, planning to become pregnant, and all medications and supplements you are taking.
- Repeat TSH in 4–8 weeks
- Pass free T4, if necessary free T3
- Antibodies to TPO
- Ultrasound of the thyroid gland
- Node puncture according to indications
- Tell your doctor about pregnancy and medications
Treatment and observation
For overt hypothyroidism, thyroid hormone replacement therapy is prescribed, the dose adjusted according to weight and TSH level, and monitoring is usually carried out six to eight weeks after each change. For subclinical hypothyroidism, the decision depends on TSH levels, age, symptoms and pregnancy plans - sometimes observation is sufficient. Thyrotoxicosis is treated with thyreostatics, radioactive iodine or surgery, the choice is made by the endocrinologist. You cannot change the dose on your own, stop taking the drug because you feel well, or take iodine supplements for thyrotoxicosis. For pregnant women, therapy is monitored especially carefully.
- Replacement therapy for hypothyroidism - as prescribed by a doctor
- Monitor TSH 6–8 weeks after dose change
- Observation for subclinical forms
- Thyrostatics, radioiodine or surgery for thyrotoxicosis
- Special control during pregnancy and its planning
- Do not prescribe iodine or supplements without testing