What are thyroid tests and why are they important. How do blood tests like TSH, T3, and T4 help diagnose thyroid disorders. What imaging procedures are used to evaluate thyroid function. How can thyroid antibody tests assist in identifying autoimmune thyroid conditions.

The Crucial Role of Thyroid Tests in Diagnosing Thyroid Disorders

Thyroid tests are essential diagnostic tools used to evaluate the function of the thyroid gland, a small but mighty organ located in the front of the neck. These tests are instrumental in identifying and managing various thyroid disorders, including hyperthyroidism and hypothyroidism. By measuring hormone levels and examining the gland’s structure, healthcare providers can gain valuable insights into a patient’s thyroid health.

The thyroid gland plays a pivotal role in regulating numerous bodily functions through the production of hormones. These hormones influence:

• Metabolism
• Heart rate
• Body temperature
• Energy levels
• Mood
• Digestion

Given the wide-ranging impact of thyroid hormones, accurate testing is crucial for maintaining overall health and well-being.

Understanding the TSH Test: The Primary Screening Tool for Thyroid Function

The Thyroid Stimulating Hormone (TSH) test is typically the first line of investigation when assessing thyroid function. TSH is produced by the pituitary gland and acts as a messenger, signaling the thyroid to produce and release its hormones.

Why is the TSH test so important? It serves as a sensitive indicator of thyroid function, often revealing abnormalities before other thyroid hormone levels show significant changes. Elevated TSH levels may indicate hypothyroidism, while low TSH levels can suggest hyperthyroidism.

Interpreting TSH results requires consideration of the reference range, which can vary slightly between laboratories. Generally, normal TSH levels fall between 0.4 and 4.0 mIU/L (milliunits per liter). However, optimal levels may differ based on individual factors such as age, pregnancy status, and overall health.

T3 and T4 Tests: Measuring Thyroid Hormone Levels Directly

While TSH provides valuable information about thyroid function, measuring the actual thyroid hormones – triiodothyronine (T3) and thyroxine (T4) – offers a more comprehensive picture. These tests are often performed in conjunction with TSH or as follow-up tests when TSH levels are abnormal.

T4 is the primary hormone produced by the thyroid gland, while T3 is the more active form. Both hormones exist in two states within the bloodstream:

1. Free (unbound) hormones
2. Bound hormones (attached to proteins)

Most thyroid tests measure the free hormone levels, as these represent the active, available hormones. Free T4 and Free T3 tests provide a more accurate assessment of thyroid function compared to total T4 and T3 measurements.

Thyroid Antibody Tests: Uncovering Autoimmune Thyroid Disorders

Autoimmune thyroid disorders occur when the immune system mistakenly attacks the thyroid gland. Thyroid antibody tests help identify these conditions by measuring specific antibodies in the blood. The most common antibodies tested include:

• Thyroid peroxidase antibodies (TPOAb)
• Thyroglobulin antibodies (TgAb)
• Thyroid stimulating hormone receptor antibodies (TRAb)

Elevated levels of these antibodies can indicate autoimmune thyroid diseases such as Hashimoto’s thyroiditis or Graves’ disease. These tests are particularly useful in diagnosing subclinical thyroid dysfunction and predicting the risk of future thyroid problems.

Imaging Tests for Thyroid Evaluation: Beyond Blood Work

While blood tests provide crucial information about thyroid function, imaging tests offer valuable insights into the gland’s structure and activity. These tests are particularly useful in cases where physical examination or blood tests suggest thyroid abnormalities.

Thyroid Ultrasound

Thyroid ultrasound is a non-invasive imaging technique that uses high-frequency sound waves to create detailed images of the thyroid gland. It can reveal:

• The size and shape of the thyroid
• The presence of nodules or cysts
• Changes in thyroid tissue composition

Ultrasound guidance is also used during fine-needle aspiration biopsies of suspicious thyroid nodules.

Thyroid Scan and Radioactive Iodine Uptake Test

These nuclear medicine tests involve the administration of a small amount of radioactive iodine to evaluate thyroid function and structure. The thyroid scan provides information about the gland’s size, shape, and position, as well as the presence of nodules. The radioactive iodine uptake test measures how much iodine the thyroid absorbs, helping to differentiate between various causes of hyperthyroidism.

CT Scans and MRI

Computed tomography (CT) scans and magnetic resonance imaging (MRI) may be used in specific cases to provide detailed cross-sectional images of the thyroid and surrounding structures. These imaging modalities are particularly useful when evaluating large goiters or suspected thyroid cancer.

Interpreting Thyroid Test Results: A Holistic Approach

Interpreting thyroid test results requires a comprehensive approach, considering multiple factors beyond just the numerical values. Healthcare providers take into account:

• The patient’s symptoms and medical history
• The relationship between different test results
• Age-specific reference ranges
• Pregnancy status
• Medications that may affect thyroid function or test results

It’s important to note that a single abnormal test result does not necessarily indicate thyroid disease. Repeat testing or additional investigations may be necessary to confirm a diagnosis.

Special Considerations in Thyroid Testing

Certain populations require special attention when it comes to thyroid testing. These include:

Pregnant Women

Thyroid function changes during pregnancy, and normal reference ranges differ from those of non-pregnant individuals. Regular monitoring of thyroid function is crucial during pregnancy, as both hyper- and hypothyroidism can affect fetal development and maternal health.

Newborns

Newborn screening for congenital hypothyroidism is standard practice in many countries. Early detection and treatment of thyroid disorders in infants are essential for proper growth and neurological development.

Older Adults

Thyroid function can change with age, and symptoms of thyroid disorders may be subtle or attributed to other conditions. Regular screening and appropriate interpretation of results are important in this population.

Emerging Trends in Thyroid Testing and Research

As our understanding of thyroid physiology evolves, so do the approaches to thyroid testing. Some emerging areas of interest include:

• The role of reverse T3 in thyroid disorders
• Genetic testing for hereditary thyroid conditions
• The impact of environmental factors on thyroid function
• Development of more sensitive and specific thyroid antibody tests
• Exploration of novel biomarkers for thyroid cancer detection

Ongoing research in these areas promises to enhance our ability to diagnose and manage thyroid disorders more effectively in the future.

Thyroid testing plays a vital role in maintaining overall health and well-being. By combining blood tests, imaging studies, and a thorough clinical evaluation, healthcare providers can accurately diagnose and manage thyroid disorders. As our understanding of thyroid function continues to grow, so does our ability to provide personalized and effective care for individuals with thyroid conditions.

Regular thyroid check-ups, especially for those at higher risk of thyroid disorders, can lead to early detection and improved outcomes. By staying informed about thyroid health and working closely with healthcare providers, individuals can take proactive steps to maintain optimal thyroid function and overall wellness.

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

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  Also in Spanish

• Thyroid Antibodies

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  Also in Spanish

• Thyroid Function Tests

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  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)

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• Thyroxine (T4) Test

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  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)

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• ClinicalTrials. gov: Thyroid Function Tests

  (National Institutes of Health)

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

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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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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.