What are thyroid tests and why are they important. How do different thyroid blood tests work. What imaging tests are used to examine the thyroid gland. How do doctors diagnose and monitor thyroid disorders. What should patients expect during thyroid testing procedures.

The Crucial Role of Thyroid Hormones in Body Function

The thyroid gland, a small butterfly-shaped organ located in the front of the neck, plays a vital role in regulating numerous bodily functions. This endocrine powerhouse produces hormones that influence nearly every organ system, controlling crucial processes such as:

• Metabolism and energy utilization
• Heart rate and cardiovascular function
• Respiratory rate
• Body weight and temperature regulation
• Digestive processes
• Mood and cognitive function

Given the thyroid’s far-reaching effects, maintaining proper hormone levels is essential for overall health and well-being. Thyroid tests serve as invaluable tools for healthcare providers to assess gland function, diagnose disorders, and monitor treatment efficacy.

Unveiling the Spectrum of Thyroid Blood Tests

Blood tests form the cornerstone of thyroid evaluation, offering insights into hormone levels and potential autoimmune activity. The most common thyroid blood tests include:

TSH (Thyroid-Stimulating Hormone) Test

The TSH test is typically the first-line screening tool for thyroid function. Why is TSH so important? This hormone, produced by the pituitary gland, acts as a messenger to stimulate thyroid hormone production. Elevated TSH levels often indicate an underactive thyroid (hypothyroidism), while low levels may suggest an overactive gland (hyperthyroidism).

T3 and T4 Tests

These tests measure the levels of the two primary thyroid hormones: triiodothyronine (T3) and thyroxine (T4). How do T3 and T4 differ? T4 is the main hormone produced by the thyroid, while T3 is the more biologically active form. Analyzing both provides a comprehensive picture of thyroid function and can help pinpoint specific disorders.

Thyroid Antibodies Test

Autoimmune thyroid disorders, such as Hashimoto’s thyroiditis and Graves’ disease, involve the production of antibodies that target thyroid tissue. The thyroid antibodies test detects these immune markers, aiding in the diagnosis of autoimmune conditions and guiding treatment strategies.

Advanced Imaging Techniques for Thyroid Evaluation

While blood tests offer valuable biochemical data, imaging studies provide crucial structural and functional information about the thyroid gland. The most commonly employed imaging techniques include:

CT (Computed Tomography) Scans

CT scans use X-rays to create detailed cross-sectional images of the thyroid and surrounding structures. When might a CT scan be necessary? These scans are particularly useful for assessing thyroid nodules, evaluating the extent of thyroid cancer, and planning surgical interventions.

Thyroid Ultrasound

Ultrasound imaging employs high-frequency sound waves to visualize the thyroid gland’s structure. This non-invasive technique excels at detecting and characterizing thyroid nodules, measuring gland size, and guiding fine-needle aspiration biopsies.

Nuclear Medicine Tests

Nuclear medicine studies offer unique insights into thyroid function and metabolism. Two primary nuclear tests are used:

1. Thyroid Scan: This procedure involves administering a small amount of radioactive iodine or technetium-99m. The resulting images reveal the gland’s size, shape, and position while highlighting areas of increased or decreased activity.
2. Radioactive Iodine Uptake (RAIU) Test: The RAIU test measures how efficiently the thyroid absorbs iodine, a crucial component of thyroid hormone production. This information helps differentiate between various causes of hyperthyroidism and guides treatment decisions.

Decoding Thyroid Test Results: What Do the Numbers Mean?

Interpreting thyroid test results requires a nuanced understanding of reference ranges and the interplay between different hormones. How do healthcare providers analyze these results?

• TSH Levels: Normal TSH typically falls between 0.4 and 4.0 mIU/L, though ranges may vary slightly between laboratories. Values outside this range warrant further investigation.
• T4 and T3 Levels: These are interpreted in conjunction with TSH. For instance, high TSH with low T4 suggests primary hypothyroidism, while low TSH with high T4 or T3 indicates hyperthyroidism.
• Antibody Levels: The presence of thyroid antibodies, even with normal TSH and hormone levels, may indicate an increased risk of future thyroid dysfunction.

It’s crucial to note that thyroid function exists on a spectrum, and results must be considered in the context of an individual’s symptoms, medical history, and other factors.

Thyroid Disorders: From Diagnosis to Management

Thyroid tests play a pivotal role in diagnosing and managing various thyroid disorders. How do these tests guide clinical decision-making?

Hypothyroidism

Characterized by an underactive thyroid, hypothyroidism is typically diagnosed when TSH levels are elevated and T4 levels are low. Treatment usually involves thyroid hormone replacement therapy, with ongoing monitoring to ensure optimal dosing.

Hyperthyroidism

An overactive thyroid results in low TSH and elevated T4 or T3 levels. Additional tests, such as thyroid antibodies and RAIU, help determine the underlying cause (e.g., Graves’ disease, toxic nodules). Treatment options may include antithyroid medications, radioactive iodine therapy, or surgery.

Thyroid Nodules and Cancer

Thyroid function tests, combined with imaging studies and fine-needle aspiration biopsies, guide the evaluation of thyroid nodules. While most nodules are benign, certain characteristics may raise suspicion for malignancy, necessitating further investigation or surgical intervention.

Emerging Trends in Thyroid Testing and Diagnosis

The field of thyroid diagnostics continues to evolve, with ongoing research and technological advancements enhancing our understanding and approach to thyroid disorders. What are some cutting-edge developments in thyroid testing?

• Molecular Testing: Genetic analysis of thyroid nodule samples can help refine cancer risk assessment, potentially reducing unnecessary surgeries.
• Artificial Intelligence in Imaging: Machine learning algorithms are being developed to assist in the interpretation of thyroid ultrasounds, improving nodule classification accuracy.
• Personalized Reference Ranges: Research suggests that individual-specific TSH ranges may provide more accurate assessments of thyroid function than population-based ranges.
• Novel Biomarkers: Ongoing studies are exploring new blood markers that could offer additional insights into thyroid health and function.

Patient Preparation and Expectations for Thyroid Testing

Proper preparation is key to ensuring accurate thyroid test results. What should patients know before undergoing thyroid testing?

Blood Tests

• Fasting is typically not required for most thyroid blood tests.
• Certain medications, including biotin supplements, can interfere with test results. Patients should inform their healthcare provider about all medications and supplements they are taking.
• For optimal accuracy, blood samples are usually drawn in the morning, as TSH levels can fluctuate throughout the day.

Imaging Tests

• Patients may need to avoid iodine-rich foods and medications before nuclear medicine tests.
• Jewelry and metal objects should be removed before CT scans and some other imaging procedures.
• Pregnant women should inform their healthcare provider, as certain imaging tests may not be recommended during pregnancy.

By understanding the importance of thyroid tests and knowing what to expect, patients can actively participate in their thyroid health management and work collaboratively with their healthcare team to achieve optimal outcomes.

Thyroid Tests: MedlinePlus

Also called: Thyroid panel

Your thyroid is a small, butterfly-shaped gland in the front of your neck. It makes hormones that control the way the body uses energy. These hormones affect nearly every organ in your body and control many of your body’s most important functions. For example, they affect your breathing, heart rate, weight, digestion, and moods.

Thyroid tests check how well your thyroid is working. They are also used to diagnose and help find the cause of thyroid diseases such as hyperthyroidism and hypothyroidism. Thyroid tests include blood tests and imaging tests.

Blood tests for your thyroid include:

• TSH. It measures thyroid-stimulating hormone. This is usually the first test your healthcare provider will order.
• T3 and T4.They measure the level of the different thyroid hormones in your blood.
• Thyroid antibodies test. It measures certain thyroid antibodies (markers in the blood). This test may help diagnose autoimmune thyroid disorders.

Imaging tests include:

• CT scans
• Ultrasound
• Nuclear medicine tests, including:
  • Thyroid scan. It uses small amounts of radioactive material to create a picture of the thyroid, showing its size, shape, and position. It can help find the cause of hyperthyroidism and check for thyroid nodules (lumps in the thyroid).
  • Radioactive iodine uptake test, or thyroid uptake test. It checks how well your thyroid is working and can help find the cause of hyperthyroidism.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

• Calcitonin Test

  (National Library of Medicine)

  Also in Spanish

• Thyroid Antibodies

  (National Library of Medicine)

  Also in Spanish

• Thyroid Function Tests

  (American Thyroid Association)

  Also in Spanish

• Thyroid Scan and Uptake

  (American College of Radiology; Radiological Society of North America)

  Also in Spanish

• Thyroid Tests

  (Nemours Foundation)

• Thyroid Tests

  (National Institute of Diabetes and Digestive and Kidney Diseases)

  Also in Spanish

• Thyroxine (T4) Test

  (National Library of Medicine)

  Also in Spanish

• Triiodothyronine (T3) Tests

  (National Library of Medicine)

  Also in Spanish

• TSH (Thyroid-stimulating hormone) test

  (National Library of Medicine)

  Also in Spanish

• Ultrasound – Thyroid

  (American College of Radiology; Radiological Society of North America)

  Also in Spanish

• ClinicalTrials. gov: Thyroid Function Tests

  (National Institutes of Health)

• Article: Circulating free T3 associates longitudinally with cardio-metabolic risk factors in euthyroid. ..

• Article: Assessment of thyroid function tests in patients with chronic obstructive pulmonary…

• Article: The impact of covid-19 on thyroid function tests in pregnancy.

• Thyroid Tests — see more articles

Sensitive thyroid-stimulating hormone assays: clinical applications and limitations

Review

. 1988 Sep;14(9):26-33.

E T De Los Santos 
¹
, E L Mazzaferri

Affiliations

Affiliation

• ¹ Division of Endocrinology and Metabolism, Ohio State University, Columbus 43210.

• PMID:

  3064960

Review

E T De Los Santos et al.

Compr Ther.

1988 Sep.

. 1988 Sep;14(9):26-33.

Authors

E T De Los Santos 
¹
, E L Mazzaferri

Affiliation

• ¹ Division of Endocrinology and Metabolism, Ohio State University, Columbus 43210.

• PMID:

  3064960

Abstract

Sensitive TSH assays have important applications in various conditions, including the diagnosis of hypothyroidism and hyperthyroidism, monitoring thyroid hormone therapy and treated thyrotoxic patients, and evaluating thyroid dysfunction in nonthyroidal illnesses and pregnancy. Interpretation of the TSH value should be made with a clear understanding of its limitations. TSH may be inappropriately secreted by pituitary tumors and by pituitary dysfunction due to thyroxine resistance. At present, it is uncertain whether clinically euthyroid patients with autonomously functioning thyroid nodules, or with multinodular goiters, or patients taking thyroid hormone who have suppressed TSH values, are actually euthyroid at a cellular level. Other factors that affect TSH levels are the biologic variation in its secretion, the presence of heterophilic antibodies in a patient’s serum, and various drugs. But perhaps the most important factor affecting the TSH assay is severe nonthyroidal illness in hospitalized patients. The new ultrasensitive TSH assay does not yet replace other thyroid function tests, but it is clearly emerging as an important means of screening patients for thyroid dysfunction, especially ambulatory patients without other serious illnesses. It can usually separate patients with thyroid dysfunction from euthyroid individuals. Good clinical assessment is always necessary, and other thyroid function tests are often needed. The sensitivity of these new TSH assays in the diagnosis of thyrotoxicosis and hypothyroidism is excellent; the specificity is not as good. Nonetheless, at present this test can be used in the initial diagnosis of thyroid dysfunction as outlined in Figure 2.(ABSTRACT TRUNCATED AT 250 WORDS)

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MeSH terms

Substances

Blood thyroid stimulating hormone (TSH) test

Brief description:
Thyroid-stimulating hormone (TSH) is the main regulator of thyroid function, synthesized by the pituitary gland. Its main function is to maintain a constant concentration of thyroid hormones. When their blood levels decrease, the hypothalamus releases a hormone that stimulates the secretion of TSH by the pituitary gland.

Synonyms (rus): Thyroid stimulating hormone, Thyrotropin, TSH
Synonyms (eng): Thyroid Stimulating Hormone, TSH

Units: µIU/mL (microinternational unit per milliliter)

Methods: Immunochemiluminescent assay

Test preparation:
• Do not eat for 2-3 hours before the study, you can drink clean non-carbonated water.
• Eliminate the use of steroid and thyroid hormones within 48 hours before the study (as agreed with the doctor).
• Avoid physical and emotional stress for 24 hours prior to the study.
• Do not smoke for 3 hours prior to the study.

Biomaterial type: Venous blood

Tube type: Vacuum tubes with coagulation activator and gel (Cap color: red with yellow ring)

Completion time: one business day.

Reference values:

4 months – 1 year 0.7 – 8.35 µIU/ml
1 – 6 years 0.7 – 6 µIU/ml
7 – 11 years 0.6 – 4.84 µIU/ml
12 – 20 years 0.51 – 4.3 µIU/ml
> 20 years 0.24 – 4.3 µIU/mL
During pregnancy: 1st trimester 0.33-4.59 µIU/mL
2nd trimester 0.35-4.10 µIU/ml
3rd trimester 0.21-3.15 μIU/ml

Causes of increased thyroid-stimulating hormone:
• hypothyroidism (primary and secondary),
• pituitary tumor (thyrotropinoma, basophilic adenoma),
• Hashimoto’s thyroiditis,
• syndrome of unregulated secretion of TSH,
• thyrotropin-secreting lung tumors,
• adrenal insufficiency,
• preeclampsia,
• lead poisoning,
• mental illness.

Causes of a decrease in the concentration of thyroid-stimulating hormone:
• diffuse toxic goiter,
• TSH-independent thyrotoxicosis,
• thyrotoxic adenoma (Plummer’s disease),
• hyperthyroidism of pregnant women,
• autoimmune thyroiditis with manifestations of thyrotoxicosis,
• mental illness,
• cachexia.

Code: A09.05.065

Take a blood test for TSH (Thyrotropic hormone)

Full name of the test: Thyroid Stimulating Hormone (TSH)

Thyroid-stimulating hormone is produced by the pituitary gland and is involved in the regulation of the thyroid gland. The pituitary gland itself is located in the brain and does not act directly on organs and systems, it works through “intermediaries”, which are thyroxine and triiodothyronine. At the same time, the production of TSH is controlled by a hormone produced by the hypothalamus and biogenic amines, which are derivatives of ammonia.

A change in the level of thyroid-stimulating hormone affects the synthesis of active substances reproduced by the thyroid gland, which ultimately leads to the development of a large number of pathologies.

Deviations in the work of the pituitary gland occur more often in women, therefore, this type of examination is prescribed to them more often than to the representatives of the stronger sex. Determination of the level of TSH is usually carried out in conjunction with the determination of the level of thyroid hormones.

What analysis shows

The analysis is carried out in order to assess the work of the pituitary gland and thyroid gland. Determining the level of thyroid-stimulating hormone is necessary, since this active organic substance has the ability to influence many organs and systems.

With the help of an analysis for TSH, a number of pathologies can be suspected:

• threatened miscarriage;
• disruption of the central nervous system;
• pathology of the adrenal glands;
• thyroiditis;
• pituitary tumor;
• thyroid tumor;
• toxic goiter;
• mental disorders, etc.

It is important to note that a single blood test does not make a diagnosis. The study helps to suspect abnormalities and prescribe an additional examination to confirm the diagnosis. Therefore, the choice of analysis and its interpretation should be carried out by an endocrinologist.

Indications for analysis

Material sampling for thyroid-stimulating hormone is carried out if the following abnormalities are suspected:

• pathology of the pituitary gland;
• cycle disorder in women and infertility;
• pathology of the thyroid gland;
• if symptoms of heavy metal poisoning are present.

Patients with altered TSH levels often experience the following symptoms:

• frequent depression;
• body temperature decreases for unknown reasons;
• in the absence of deviations from the myocardium, the heart rhythm is disturbed;
• with a small amount of work performed, the patient is very tired;
• muscle work worsens;
• loss of sexual desire;
• hair loss in large quantities, most often ending in baldness. ;
• in men, a change in the level of the hormone leads to a decrease in potency.

As a rule, the study is prescribed by a doctor, based on the data obtained about the patient’s well-being.

Preparation for procedure

An analysis for TSH requires preliminary preparation; without this, data that really reflects the state of the body cannot be obtained.

Before taking blood, the patient will have to follow the following recommendations:

• Avoid alcoholic beverages, including those with low alcohol content.
• During the day it will be necessary to introduce a diet that excludes the use of fatty, spicy fried foods.
• The analysis should be taken in a calm psycho-emotional state, so even minimal stress will have to be avoided, especially on the day of the examination.
• The last meal on the eve of the study should take place no later than eight o’clock in the evening.
• Blood can not be donated after undergoing ultrasound, computed tomography and fluorography.
• All non-essential drugs should be discontinued. It is desirable to use these medicines for their intended purpose after blood sampling. If this is not possible, then the name of the drug and its dose are indicated on the referral.

If necessary, re-sampling of the material is allowed to clarify the results obtained. An indispensable condition for re-examination: blood must be taken at the same time as the previous sample.

Causes of false results

Various external and internal factors can change the true values. First of all, the intake of certain drugs affects the volume of hormones.

Erroneous data can be obtained when blood samples are incorrectly obtained and used by medical personnel.

Test results may be affected by pregnancy.

How the analysis is done

For research, venous blood is used. An immunochemical method is used to determine the level of the hormone. This method of examination is used not only to determine the level of TSH.

The convenience of this method lies in the fact that a special component is introduced into the material, which plays the role of a label. It forms an antigen-antibody compound, which makes it easy to detect and count.

If intravenous infusion of drugs was performed shortly before the study, this arm cannot be used to take the material. Doctors recommend taking blood from a vein in the other arm.

Interpretation of the result

It is important to understand that the interpretation of test data is the prerogative of the attending physician. It is strictly forbidden to use the received information for self-diagnosis and
self-treatment. The specialist makes an accurate diagnosis, based both on the test data and by collecting information from the patient, using other sources, anamnesis, etc.
d.

Units of measurement in the Independent laboratory: honey/l.

Alternate units: µU/mL = mU/L.

Unit conversion: µU/mL = mU/L.

Reference
values ​​

9 0190

Age	TSH level, mU/l
4 days – 6 months	0. 73-4.77
6 months – 14 years	0.7-4, 17
14-19 years old	0.47-3.41
> 19 years	0.4 -4.0

Guideline pregnancy limits:

• first
  trimester: 0.1-2.5 mU/l
• second trimester: 0.2-3.0 mU/l
• third trimester: 0.3-3.0 mU/l

Increased values:

1. Primary type of hypothyroidism (iodine deficiency, autoimmune type of thyroiditis; hereditary hormone production defects, congenital
pathology of the thyroid organ, the consequences of surgical removal of part of the thyroid gland).

2. Subclinical type of hypothyroidism.

3. Thyroiditis of subacute type (recovery period).

4. Ectopic release of TSH (tumors of the breast, lungs).

5. TSH-releasing pituitary adenoma (in rare cases).

6. Somatic diseases in severe stages (recovery period).

7. Thyroid hormone resistance syndrome.

8. Oncological processes in the thyroid gland.

9. Taking drugs such as: beta-blockers (metoprolol, atenolol, propranolol), neuroleptics (phenothiazine derivatives,
aminoglutethimide), radiopaque agents, clomiphene, amiodarone, iodine-containing drugs, antiemetics (motilium, metoclopramide), anticonvulsants
(carbamazepine, phenytoin), furosemide, lithium salts.

Decrease in values:

1. Primary type of hyperthyroidism (diffuse goiter (toxic), multinodular (toxic) goiter, adenoma (toxic,) thyroid nodes (functioning autonomously).

2. Subclinical type of hyperthyroidism.

3. When autoimmune type of thyroiditis (transient thyrotoxicosis)

4. Iatrogenic (artificial hyperthyroidism)

5. Hyperthyroidism during pregnancy

6. Secondary or pituitary type of hypothyroidism

7. Fasting, diets,
stress.

8. Severe non-thyroid diseases.

9. Hypothalamic-pituitary insufficiency.

10. Tumor processes in
pituitary gland.