What are normal thyroid hormone levels. How do TSH, T4, and T3 tests work. Why are thyroid function tests important for diagnosing thyroid disorders. What do abnormal thyroid test results indicate.

The Fundamentals of Thyroid Hormone

Thyroid hormone plays a crucial role in maintaining overall health and well-being. Produced by the butterfly-shaped thyroid gland located in the lower front of the neck, this hormone regulates various bodily functions, including energy utilization, temperature regulation, and the proper functioning of vital organs such as the brain, heart, and muscles.

There are two primary forms of thyroid hormone:

• Thyroxine (T4): The main form circulating in the blood, accounting for about 95% of thyroid hormone
• Triiodothyronine (T3): The active form, which makes up approximately 5% of circulating thyroid hormone

T4 is converted to T3 through the removal of an iodine atom, primarily in the liver and specific tissues where T3 exerts its effects. This conversion process is essential for the hormone to carry out its biological functions effectively.

The Role of TSH in Thyroid Function

Thyroid Stimulating Hormone (TSH) is a key player in regulating thyroid hormone production. Produced by the pituitary gland in the brain, TSH acts as a messenger between the pituitary and the thyroid gland. Its primary function is to stimulate the thyroid to produce more thyroid hormone when levels are low.

The pituitary gland operates like a thermostat, continuously monitoring thyroid hormone levels in the bloodstream. When levels drop, it increases TSH production to signal the thyroid to produce more hormone. Conversely, when thyroid hormone levels rise above a certain threshold, TSH production is suppressed.

How does TSH testing help diagnose thyroid disorders?

TSH testing is considered the gold standard for initial thyroid function assessment. It serves as an early warning system, often detecting abnormalities before actual thyroid hormone levels become too high or too low. Endocrinologists rely on a combination of TSH and thyroid hormone tests to gain a comprehensive understanding of thyroid function.

Decoding TSH Test Results

TSH tests are widely available and frequently used to evaluate thyroid function. The results can provide valuable insights into the thyroid’s performance:

• High TSH levels: Indicate that the thyroid gland is not producing enough thyroid hormone, a condition known as primary hypothyroidism
• Low TSH levels: Usually suggest that the thyroid is producing excessive amounts of thyroid hormone, a condition called hyperthyroidism
• Normal TSH levels: In most healthy individuals, this indicates proper thyroid function

It’s important to note that in rare cases, a low TSH may result from a pituitary gland abnormality, preventing it from producing sufficient TSH to stimulate the thyroid. This condition is known as central hypothyroidism.

Understanding T4 Tests and Their Significance

T4 tests measure the levels of thyroxine in the blood. There are two main types of T4 tests:

1. Total T4 test: Measures both bound and free thyroxine in the blood
2. Free T4 test: Measures only the unbound thyroxine, which is able to enter and affect body tissues

What factors can influence T4 test results?

Several factors can affect Total T4 levels, including:

• Medications
• Medical conditions that alter thyroid hormone binding proteins
• Pregnancy
• Liver disease
• Hepatitis C virus infection

These factors can lead to increased thyroid hormone binding proteins, resulting in elevated Total T4 levels. Conversely, testosterone, androgens, and anabolic steroids can decrease thyroid hormone binding proteins, leading to lower Total T4 levels.

In certain situations, such as pregnancy, an individual may have normal thyroid function but Total T4 levels outside the normal reference range. In these cases, tests measuring free T4 (FT4 or free T4 index) may provide a more accurate assessment of thyroid function.

The Importance of T3 Tests in Thyroid Evaluation

T3 tests measure triiodothyronine levels in the blood. The Total T3 test assesses both bound and free fractions of T3. These tests are particularly useful in specific scenarios:

• Supporting a diagnosis of hyperthyroidism
• Determining the severity of hyperthyroidism
• Providing diagnostic information in certain thyroid diseases where T3 and T4 proportions change

How do T3 levels differ in various thyroid conditions?

T3 levels can provide valuable insights into different thyroid disorders:

• Hyperthyroidism: Patients typically have elevated Total T3 levels
• Graves’ disease: Characterized by a pattern of increased T3 relative to T4
• Hypothyroidism: T3 levels fall late in the progression of the condition, making them less useful for routine evaluation of underactive or surgically absent thyroid glands

It’s worth noting that certain medications (e.g., steroids and amiodarone) and severe illness can decrease the body’s conversion of T4 to T3, resulting in a lower proportion of T3.

Interpreting Thyroid Test Results: A Holistic Approach

When evaluating thyroid function, it’s crucial to consider multiple factors and test results together. Endocrinologists use their expertise to interpret these results in the context of an individual’s medical history, symptoms, and other relevant factors.

Why is a combination of thyroid tests often necessary?

A single thyroid test may not always provide a complete picture of thyroid function. For example:

• TSH levels alone may not detect central hypothyroidism caused by pituitary gland issues
• Total T4 levels can be affected by changes in thyroid hormone binding proteins, potentially masking true thyroid function
• T3 tests may be more useful in diagnosing hyperthyroidism than hypothyroidism

By considering multiple test results and clinical factors, healthcare providers can make more accurate diagnoses and develop appropriate treatment plans.

Emerging Trends in Thyroid Function Testing

As our understanding of thyroid physiology advances, new testing methods and interpretations are emerging. Some recent developments include:

• Free T3 measurements: While not routinely used, these tests may provide additional insights in certain clinical scenarios
• Thyroid antibody tests: Useful in diagnosing autoimmune thyroid disorders such as Hashimoto’s thyroiditis and Graves’ disease
• Genetic testing: May help identify inherited thyroid disorders or predispositions to thyroid dysfunction

How might future advancements improve thyroid diagnostics?

Ongoing research in thyroid function testing could lead to:

• More sensitive and specific biomarkers for thyroid disorders
• Personalized reference ranges based on individual factors such as age, sex, and ethnicity
• Advanced imaging techniques for more accurate thyroid gland assessment
• Integration of artificial intelligence to assist in interpreting complex thyroid test results

These advancements may enable earlier detection of thyroid disorders and more tailored treatment approaches in the future.

Thyroid Health: Beyond the Numbers

While thyroid function tests provide valuable information, it’s essential to remember that they are just one piece of the puzzle. A holistic approach to thyroid health should consider various factors:

• Symptoms: Some individuals may experience thyroid-related symptoms even with “normal” test results
• Lifestyle factors: Diet, stress, and environmental exposures can influence thyroid function
• Other medical conditions: Certain illnesses and medications can affect thyroid hormone levels and function
• Family history: Genetic predisposition to thyroid disorders may influence interpretation of test results

How can individuals support their thyroid health?

While proper medical care is crucial, there are several ways people can promote thyroid health:

• Maintain a balanced diet rich in iodine, selenium, and zinc
• Manage stress through relaxation techniques and regular exercise
• Avoid exposure to endocrine-disrupting chemicals when possible
• Stay informed about thyroid health and discuss any concerns with a healthcare provider
• Adhere to recommended screening guidelines, especially for those at higher risk of thyroid disorders

By combining medical expertise, comprehensive testing, and proactive health measures, individuals can work towards optimal thyroid function and overall well-being.

The Future of Thyroid Care: Personalized Medicine and Patient Empowerment

As we move towards a more personalized approach to healthcare, thyroid management is likely to become increasingly tailored to individual needs. This shift may involve:

• Customized treatment plans based on genetic profiles and biomarkers
• Integration of wearable technology to monitor thyroid function in real-time
• Patient-centered care models that emphasize education and shared decision-making
• Telemedicine options for remote thyroid monitoring and management

How can patients take an active role in their thyroid health?

Empowered patients can play a crucial role in managing their thyroid health:

• Keep detailed records of symptoms, test results, and treatments
• Ask questions and seek clarification from healthcare providers
• Stay informed about new developments in thyroid research and treatment
• Participate in support groups or online communities to share experiences and resources
• Advocate for comprehensive thyroid testing when appropriate

By taking an active role in their care, patients can work collaboratively with healthcare providers to achieve optimal thyroid function and overall health.

Navigating Thyroid Disorders: From Diagnosis to Management

Understanding thyroid test results is just the beginning of the journey for many individuals with thyroid disorders. The path from diagnosis to effective management often involves several steps:

1. Initial screening and diagnosis based on symptoms and test results
2. Further testing to determine the specific type and cause of thyroid dysfunction
3. Development of a personalized treatment plan
4. Regular monitoring and adjustment of treatment as needed
5. Management of any associated conditions or complications

What are the most common thyroid disorders and their treatments?

Several thyroid disorders can be identified through thyroid function tests:

• Hypothyroidism: Typically treated with thyroid hormone replacement therapy
• Hyperthyroidism: May be managed with antithyroid medications, radioactive iodine therapy, or surgery
• Thyroid nodules: Often monitored with regular ultrasounds and may require biopsy or surgical removal
• Thyroid cancer: Treatment may involve surgery, radioactive iodine therapy, and long-term monitoring

The specific treatment approach depends on the individual’s condition, overall health, and personal preferences. Close collaboration between patients and healthcare providers is essential for successful management of thyroid disorders.

Thyroid Health Across the Lifespan

Thyroid function and the importance of thyroid testing can vary throughout an individual’s life. Understanding these changes can help ensure appropriate care at every stage:

How does thyroid function change with age?

• Newborns and infants: Screening for congenital hypothyroidism is crucial for proper development
• Children and adolescents: Thyroid disorders can affect growth and puberty
• Adults: Thyroid dysfunction can impact fertility, metabolism, and overall health
• Older adults: Thyroid disorders may present with atypical symptoms and require careful management

Regular thyroid function monitoring may be recommended for individuals with risk factors or a history of thyroid issues. Healthcare providers can advise on appropriate screening intervals based on individual circumstances.

What special considerations exist for thyroid health during pregnancy?

Thyroid function plays a critical role in pregnancy and fetal development. Key points include:

• Increased demand for thyroid hormone during pregnancy
• Need for adequate iodine intake to support thyroid function
• Potential for thyroid dysfunction to affect fetal development and pregnancy outcomes
• Importance of pre-conception thyroid screening for women with risk factors
• Close monitoring of thyroid function throughout pregnancy and postpartum period

Women who are pregnant or planning to become pregnant should discuss thyroid health with their healthcare providers to ensure optimal care for themselves and their babies.

Integrating Thyroid Health into Overall Wellness

Thyroid function is intricately connected to various aspects of health and well-being. A holistic approach to thyroid care involves considering its relationship with:

• Mental health: Thyroid dysfunction can contribute to mood disorders and cognitive issues
• Cardiovascular health: Both hypo- and hyperthyroidism can affect heart function
• Bone health: Thyroid hormones play a role in bone metabolism
• Digestive function: Thyroid disorders can influence gut motility and nutrient absorption
• Metabolic health: Thyroid hormones regulate metabolism and can affect weight and energy levels

How can individuals balance thyroid health with other wellness goals?

Maintaining thyroid health while pursuing overall wellness involves:

• Regular check-ups and thyroid function tests as recommended by healthcare providers
• Adopting a balanced diet that supports thyroid function and general health
• Engaging in regular physical activity appropriate for individual fitness levels
• Managing stress through mindfulness practices, relaxation techniques, or counseling
• Prioritizing sleep and maintaining a consistent sleep schedule
• Staying informed about the interplay between thyroid health and other aspects of well-being

By taking a comprehensive approach to health that includes attention to thyroid function, individuals can work towards achieving optimal overall wellness and quality of life.

Normal Thyroid Hormone Levels | UCLA Health

What is thyroid hormone?

Thyroid hormone is made by the thyroid gland, a butterfly-shaped endocrine gland normally located in the lower front of the neck. Thyroid hormone is released into the blood where it is carried to all the tissues in the body. It helps the body use energy, stay warm and keeps the brain, heart, muscles, and other organs working as they should.

Thyroid hormone exists in two main forms: thyroxine (T4) and triiodothyronine (T3). T4 is the primary form of thyroid hormone circulating in the blood (about 95%). To exert its effects, T4 is converted to T3 by the removal of an iodine atom; this occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. T3 normally accounts for about 5% of thyroid hormone circulating in the blood.

Most thyroid hormone in the blood is bound by protein, while only a small fraction is “free” to enter tissues and have a biologic effect. Thyroid tests may measure total (protein bound and free) or free hormone levels.

Production of thyroid hormone by the thyroid gland is controlled by the pituitary, another endocrine gland in the brain. The pituitary releases Thyroid Stimulating Hormone (abbreviated TSH) into the blood to stimulate the thyroid to make more thyroid hormone. The amount of TSH that the pituitary sends into the bloodstream depends on the amount of thyroid hormone in the body. Like a thermostat, if the pituitary senses low thyroid hormone, then it produces more TSH to tell the thyroid gland to produce more. Once the T4 in the bloodstream goes above a certain level, the pituitary’s production of TSH is shut off. In this way, the pituitary senses and controls thyroid gland production of thyroid hormone. Endocrinologists use a combination of thyroid hormone and TSH testing to understand thyroid hormone levels in the body.

What is a TSH test?

Thyroid tests
Blood tests to measure low or high TSH levels are readily available and widely used. Not all thyroid tests are useful in all situations.

TSH Test
The best way to initially test thyroid function is to measure the TSH (Thyroid Stimulating Hormone) level in a blood sample. Changes in TSH can serve as an “early warning system” — often occurring before the actual level of thyroid hormones in the body becomes too high or too low.

A high TSH level indicates that the thyroid gland is not making enough thyroid hormone (primary hypothyroidism). On the other hand, a low TSH level usually indicates that the thyroid is producing too much thyroid hormone (hyperthyroidism). Occasionally, a low TSH may result from an abnormality in the pituitary gland, which prevents it from making enough TSH to stimulate the thyroid (central hypothyroidism). In most healthy individuals, a normal TSH value means that the thyroid is functioning properly.

What is a T4 test?

T4 Tests
A Total T4 test measures the bound and free thyroxine (T4) hormone in the blood. A Free T4 measures what is not bound and able to freely enter and affect the body tissues.

What does it mean if T4 levels are abnormal?
Importantly, Total T4 levels are affected by medications and medical conditions that change thyroid hormone binding proteins. Estrogen, oral contraceptive pills, pregnancy, liver disease, and hepatitis C virus infection are common causes of increased thyroid hormone binding proteins and will result in a high Total T4. Testosterone or androgens and anabolic steroids are common causes of decreased thyroid hormone binding proteins and will result in a low Total T4.

In some circumstances, like pregnancy, a person may have normal thyroid function but Total T4 levels outside of the normal reference range. Tests measuring free T4 – either a free T4 (FT4) or free T4 index (FTI) – may more accurately reflect how the thyroid gland is functioning in these circumstances. An endocrinologist can determine when thyroid disease is present in the context of abnormal thyroid binding proteins.

What is a T3 test?

T3 Tests
T3 tests measure triiodothyronine (T3) levels in the blood. A Total T3 test measures the bound and free fractions of triiodothyronine. Hyperthyroid patients typically have an elevated Total T3 level. T3 tests can be used to support a diagnosis of hyperthyroidism and can determine the severity.

In some thyroid diseases, the proportions of T3 and T4 in the blood change and can provide diagnostic information. A pattern of increased T3 vs T4 is characteristic of Graves’ disease. On the other hand, medications like steroids and amiodarone, and severe illness can decrease the amount of thyroid hormone the body converts from T4 to T3 (active form) resulting in a lower proportion of T3.

T3 levels fall late during hypothyroidism and therefore are not routinely used to evaluate patients with underactive or surgically absent thyroid glands.

Measurement of Free T3 is possible but is often not reliable and therefore may not be helpful.

What is a normal thyroid (hormone) level?

To assess thyroid hormone status for low or high TSH levels we use TSH and FT4 tests. The normal value for a laboratory test is determined by measuring the hormone in a large population of healthy individuals and finding the normal reference range. Normal ranges for thyroid tests may vary slightly among different laboratories, and typical ranges for common tests are given below.

TSH normal values are 0.5 to 5.0 mIU/L. Pregnancy, a history of thyroid cancer, history of pituitary gland disease, and older age are some situations when TSH is optimally maintained in a different range as guided by an endocrinologist.

FT4 normal values are 0.7 to 1.9ng/dL. Individuals taking medications that modify thyroid hormone metabolism and those with a history of thyroid cancer or pituitary disease may be optimally managed with a different normal FT4 range.

Total T4 and Total T3 levels measure bound and free thyroid hormone in the blood. These levels are influenced by many factors that affect protein levels in the body, including medications, sex hormones, and liver disease.
A normal Total T4 level in adults ranges from 5.0 to 12.0μg/dL.
A normal Total T3 level in adults ranges from 80-220 ng/dL.

Free T3 assays are often unreliable and not routinely used to assess thyroid function.

What does it mean if my thyroid levels are abnormal?

Lab results	Consider…
High TSH, low thyroid hormone level	Primary hypothyroidism
High TSH, normal thyroid hormone level	Subclinical hypothyroidism
Low TSH, high thyroid hormone level	Primary hyperthyroidism
Low TSH, normal thyroid hormone level	Early or mild hyperthyroidism
Low TSH, high thyroid hormone level Followed by… High TSH, low thyroid hormone level	Thyroiditis (Thyroid Inflammation)
Low TSH, low thyroid hormone level	Pituitary disease

Patterns of thyroid tests associated with thyroid disease

Primary Hypothyroidism
A high TSH and low thyroid hormone level (e. g. low FT4) can indicate primary hypothyroidism. Primary hypothyroidism occurs when the thyroid gland makes too little thyroid hormone. Symptoms of hypothyroidism can include feeling cold, constipation, weight gain, slowed thinking, and decreased energy.
Causes of primary hypothyroidism include:

• Autoimmune thyroid disease, including Hashimoto’s thyroiditis
• Thyroid gland dysfunction due to a medication (e.g. amiodarone, tyrosine kinase inhibitors, or cancer immunotherapy)
• Removal of all or part of the thyroid gland
• Radiation injury to the thyroid (e.g. external beam radiation, radioactive iodine ablation treatment)
• Excess treatment with anti-thyroid medications (e.g. methimazole, propylthiouracil)

Early or mild hypothyroidism may present as a persistently high TSH and a normal FT4 hormone level. This pattern is called subclinical hypothyroidism and your doctor may recommend treatment. Over time, untreated subclinical hypothyroidism can contribute to heart disease.

It is important to remember that normal TSH levels in older individuals (ages 70 and above) are higher than the normal ranges for younger individuals.

Primary Hyperthyroidism
A low TSH and a high thyroid hormone level (e.g. high FT4) can indicate primary hyperthyroidism. Primary hyperthyroidism occurs when the thyroid gland makes or releases too much thyroid hormone. Symptoms of hyperthyroidism can include tremors, palpitations, restlessness, feeling too warm, frequent bowel movements, disrupted sleep, and unintentional weight loss.
Causes of primary hyperthyroidism include:

• Graves’ disease
• Toxic or autonomously functioning thyroid nodule
• Multinodular goiter
• Thyroid inflammation (called thyroiditis) early in the course of disease
• Thyroid gland dysfunction due to a medication (e.g. amiodarone or cancer immunotherapy)
• Excess thyroid hormone therapy

Early or mild hyperthyroidism may present as a persistently low TSH and a normal FT4 hormone level. This pattern is called subclinical hyperthyroidism and your doctor may recommend treatment. Over time, untreated subclinical hyperthyroidism can worsen osteoporosis and contribute to abnormal heart rhythms.

Thyroiditis
Thyroid inflammation, also called thyroiditis, causes injury to the thyroid gland and release of thyroid hormone. Individuals with thyroiditis usually have a brief period of hyperthyroidism (low TSH and high FT4 or Total T4) followed by development of hypothyroidism (high TSH and low FT4 or Total T4) or resolution.

Some forms of thyroiditis are transient, like post-partum thyroiditis or thyroiditis following an infection, and often resolve on their own without need for medication.

Other forms of thyroiditis, like thyroiditis resulting from cancer immunotherapy, interferon alpha, or tyrosine kinase inhibitors, usually result in permanent hypothyroidism and require long term treatment with thyroid hormone replacement.

Your endocrinologist will monitor your thyroid tests during thyroiditis and can help determine if you need short- and long-term medications to balance your thyroid function and control any symptoms.

Central Hypothyroidism
A low TSH and a low FT4 may indicate pituitary disease. Detection of central hypothyroidism should prompt your doctor to check for problems in other pituitary hormones, an underlying cause, and you may need imaging tests to look at the pituitary gland.

Central hypothyroidism is treated with thyroid hormone replacement. Importantly, adequacy of thyroid replacement in central hyperthyroidism is assessed with FT4 and Total T4 tests not TSH as in primary hyperthyroidism, and deficiency in stress hormone cortisol should be assessed before starting thyroid treatment to prevent an adrenal crisis. 

Causes of central hypothyroidism include pituitary gland disease, such as a pituitary mass or tumor, history of pituitary surgery or radiation, pituitary inflammation (called hypophysitis) resulting from autoimmune disease or cancer immunotherapy, and infiltrative diseases.

Rare causes of abnormal thyroid function
Thyroid hormone resistance
Iodine induced hyperthyroidism
TSH-secreting tumor (TSH-oma)
Germ cell tumors
Trophoblastic disease
Infiltrative diseases, such as systemic scleroderma, hemochromatosis, or amyloidosis.

When abnormal thyroid function tests are not due to thyroid disease

While blood tests to measure thyroid hormones and thyroid stimulating hormone (TSH) are widely available, it is important to remember that not all tests are useful in all circumstances and many factors including medications, supplements, and non-thyroid medical conditions can affect thyroid test results. An endocrinologist can help you make sense of thyroid test results when there is a discrepancy between your results and how you feel. A good first step is often to repeat the test and ensure there are no medications that might interfere with the test results. Below are some common reasons for mismatch between thyroid tests and thyroid disease.

Non-thyroidal illness
Significant illness, such as an infection, cancer, heart failure, or kidney disease, or recent recovery from an illness can cause transient changes in the TSH. Fasting or starvation can also cause a low TSH. An endocrinologist can help to interpret changes in thyroid function tests in these circumstances to distinguish non-thyroid illness from true thyroid dysfunction.

Test interference
Biotin, a common supplement for hair and nail growth, interferes with many thyroid function tests and can lead to inaccurate results. Endocrinologists recommend stopping biotin supplements for 3 days before having a blood test for thyroid function.

Individuals who have exposure to mice, like laboratory researchers and veterinarians, may develop antibodies against mouse proteins in their blood. These antibodies cross react with reagents in multiple thyroid function tests and cause unpredictable results. A specialized assay can accurately measure thyroid hormone levels and TSH in this circumstance.

I don’t feel well, but my thyroid tests are normal

Thyroid blood tests are generally accurate and reliable. If you do not have low or high TSH levels and your thyroid tests are normal, your symptoms may not be related to thyroid disease, and you may want to seek additional evaluation with your primary care physician.

How is hypothyroidism treated?

What is thyroid medication?

Thyroid Hormone Treatment
Levothyroxine is the standard of care in thyroid hormone replacement therapy and treatment of hypothyroidism. Levothyroxine (also called LT4) is equivalent to the T4 form of naturally occurring thyroid hormone and is available in generic and brand name forms.

How do I take levothyroxine?
To optimize absorption of your thyroid medication, it should be taken with water at a regular time each day. Multiple medications and supplements decrease absorption of thyroid hormone and should be taken 3–4 hours apart, including calcium and iron supplements, proton pump inhibitors, soy, and multivitamins with minerals. Because of the way levothyroxine is metabolized by the body, your doctor may ask you to take an extra pill or skip a pill on some days of the week. This helps us to fine tune your medication dose for your body and should be guided by an endocrinologist.

For patients with celiac disease (autoimmune disease against gluten) or gluten sensitivity, a gluten free formulation of levothyroxine is available. Some individuals may have genetic variant that affects how the body converts T4 to T3 and these individuals may benefit from the addition of a small dose of triiodothyronine.

Liothyronine is replacement T3 (triiodothyronine) thyroid hormone. This medication has a short half-life and is taken twice per day or in combination with levothyroxine. Liothyronine alone is not used for treatment of hypothyroidism long term.

Other formulations of thyroid hormone replacement include natural or desiccated thyroid hormone extracts from animal sources. Natural or desiccated thyroid extract preparations have greater variability in the dose of thyroid hormone between batches and imbalanced ratios if T4 vs T3. Natural or animal sources of thyroid hormone typically contain 75% T4 and 25% T3, compared to the normal human balance of 95% T4 and 5% T3. Treatment with a correct balance of T4 and T3 is important to replicate normal thyroid function and prevent adverse effects of excess T3, including osteoporosis, heart problems, and mood and sleep disturbance. An endocrinologist can evaluate symptoms and thyroid tests to help balance thyroid hormone medications.

How do I know if my thyroid dose is correct?

Monitoring thyroid levels on medication
Correct dosing of thyroid hormone is usually assessed using the same tests for diagnosis of thyroid disease, including TSH and FT4. Thyroid tests are typically checked every 4-6 weeks initially and then every 6 to 12 months once stable. In special circumstances, such as pregnancy, a history of thyroid cancer, central hypothyroidism, amiodarone therapy, or use of combination T4 and T3 thyroid hormone replacement, your endocrinologist may check different thyroid tests. Additionally, your endocrinologist will evaluate for symptoms of hyperthyroidism and hypothyroidism and perform a physical exam.

Women who are pregnant and women who may become pregnant should only be treated with levothyroxine (T4). Only T4 efficiently crosses the placenta to provide thyroid hormone to the developing fetus. Thyroid hormone is critical in early pregnancy for brain development. Normal ranges for thyroid tests in pregnancy are different and change by trimester. Women with thyroid disease in pregnancy or who are considering pregnancy should be under the care of an endocrinologist to guide therapy.

Individuals with a history of thyroid cancer, even if only a portion of the thyroid was removed, also have different target ranges for TSH and FT4 tests. Thyroid hormone replacement in these individuals is closely tied to ongoing thyroid cancer surveillance, monitoring of thyroid cancer tumor markers, and dynamic assessment of recurrence risk. These patients are optimally managed by a multidisciplinary team including an endocrinologist and endocrine surgeon.

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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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• Thyroid Antibodies

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• Thyroid Function Tests

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• Thyroid Scan and Uptake

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• Thyroid Tests

  (Nemours Foundation)

• Thyroid Tests

  (National Institute of Diabetes and Digestive and Kidney Diseases)

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• Thyroxine (T4) Test

  (National Library of Medicine)

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• 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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TSH: function, norms and deviations

Life processes in the human body are regulated by the nervous and endocrine systems. An important function in this is assigned to the hypothalamic-pituitary complex. It consists of parts of the brain that regulate the vegetative functions of the body. They produce a number of hormones that control the activity of the endocrine glands. In particular, TSH coordinates the work of the thyroid gland. It is produced by the anterior pituitary gland. In turn, thyroid hormones also perform a number of important functions. They support the metabolism of various substances, regulate the functioning of organs, systems and tissues. In children, they take part in the correct physical and mental development of the body.

The effect of TSH on the vital activity of the organism

The main function of thyroid-stimulating hormone is the mutual regulation of the synthesis of the thyroid hormones T3 and T4. If T3 and T4 free is lowered, TSH stimulates their production, and they, on the contrary, are able to inhibit the synthesis of thyroid-stimulating hormone. This process is triggered in the event of an increase in the concentration of T3 and T4. Thus, the correct hormonal balance in the body of a healthy person is maintained.
In addition, TSH regulates the production of a number of important substances, including proteins and lipids. The hormone affects the thyroid gland in several ways: vascularization, regulation of iodine absorption, increased blood flow, stimulation of hormone synthesis, and acceleration of gland growth.

Norms and deviations of TSH level

Violation of the level of TSH is possible in both women and men, but normal levels differ depending on gender. An analysis for TSH is prescribed if the doctor suspects a thyroid disease.
Reference values ​​in adults: from 0.4-0.5 mIU / l to 4.2-5 mIU / l. For children, normal rates are determined according to age. During childbearing, the allowable range of thyroid-stimulating hormone concentration depends on the gestational age. In men, the concentration of the hormone usually does not exceed 3.5 mIU / l. A variety of factors can affect TSH levels. For example, during prolonged exposure to cold, TSH is elevated, as the body increases its metabolism by 20% to adapt to extreme conditions.
Self-assessment of the results of laboratory analysis does not lead to anything good. A person comes up with a non-existent diagnosis for himself, begins to worry about this, aggravating the situation. Only a doctor can correctly interpret the results of the analysis. At the same time, he takes into account the age and gender of the person, the presence of concomitant diseases, the clinical picture and other points.

When to check TSH levels

An analysis of the thyroid gland is prescribed in case of suspicion of its dysfunction. The doctor may recommend taking it if you have symptoms such as constant weakness, depression, sleep disturbances, decreased libido, baldness, a visually noticeable enlargement of the thyroid gland, and so on. If a thyroid disease has already been identified (for example, a toxic goiter has been diagnosed), regular studies are prescribed to monitor the patient’s condition and evaluate the effectiveness of therapy.
After the age of 40, the risk of problems in the thyroid gland increases. The disease can be asymptomatic for a long time. Therefore, all people over 40 are recommended to regularly take such a blood test. The thyroid gland responds well to therapeutic treatment only in the early stages of the pathological process, so it is important to identify the disease as early as possible.

Thyroid stimulating hormone (TSH): get tested

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Author-physician:

Savchenko Svetlana Petrovna

Expert in the field of laboratory diagnostics, healthcare organization, diagnostics and treatment of therapeutic diseases.

Article publication date:
05/24/2018

Updated:
06/01/2023

What will a blood test for thyroid hormones tell about?

The thyroid hormone blood test is an essential test that helps evaluate the functioning of the thyroid gland and detect abnormalities in its function. This material will consider what indicators are given special attention when assessing the functioning of the thyroid gland.

This gland is located on the front of the neck and consists of two lobes, which are located on both sides of the trachea and are connected by an isthmus. This organ secretes 2 main hormones into the bloodstream, one of which is thyroxine. It contains 4 iodine atoms and is therefore often referred to as T4. Thyroxine is converted to triiodothyronine (T3 hormone), which contains 3 iodine atoms. It is triiodothyronine that is a biologically active substance that regulates metabolic processes in the body.

The amount of hormones T4 and T3 secreted is regulated by the pituitary gland, which is located under the brain. The pituitary gland monitors the level of thyroid hormones in the blood, much like a thermostat monitors the temperature in a room. If the level of thyroxine (T4) falls below normal, the pituitary gland immediately reacts – it produces the thyroid-stimulating hormone TSH, which causes the thyroid gland to produce more thyroxine. When the level of hormones rises beyond the norm, the pituitary gland captures this information and stops producing the hormone TSH, due to which the thyroid gland reduces the production of thyroxine.

Blood tests help the doctor detect and/or monitor diseases such as:

• Hyperthyroidism is a condition in which the gland produces too much hormones. Graves’ disease is the most common cause of hyperthyroidism.
• Hypothyroidism is a condition in which the gland does not produce enough hormones. The most common cause of hypothyroidism is Hashimoto’s disease.
• Thyroid nodules and thyroid cancer.

In order to understand whether a patient needs a blood test, doctors ask him for signs of thyroid dysfunction.

Symptoms of hyperthyroidism:

• Increased heart rate,
• Anxiety,
• Weight loss,
• Poor sleep, 9004 5
• Shaking hands,
• Weakness,
• Diarrhea,
• Heat intolerance,
• Swelling around the eyes, dryness, irritation, protrusion of the eyes.

Symptoms of hypothyroidism :

• Weight gain,
• Dry skin,
• Constipation,
• Poor cold tolerance,
• Hair loss,
• Fatigue,
• Puffy skin,
• Irregular menstrual cycle.

In addition to specific signs of hyper- and hypothyroidism, a blood test for thyroid hormones is required for the following symptoms:

• Swelling or swelling in the neck,
• Irregular or fast heart rate,
• High cholesterol,
• Osteoporosis,
• Problems conceiving a child, recurrent miscarriages, decreased libido, 9004 5
• Family history of autoimmune disease, eg – type 1 diabetes, vitiligo, etc.,
• Feeling unwell after having a baby,
• Planning for or early pregnancy, especially if you have a family or personal history of thyroid disease (including postpartum thyroiditis) or diabetes 1 type.

What tests does the thyroid panel consist of?

One or more tests are prescribed to diagnose diseases and monitor the effectiveness of treatment. The most important of them are an analysis for thyroid-stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3), as well as a test for thyroid antibodies.

TSH test (thyrotropic)

This test is the most important indicator of thyroid function. If TSH is elevated, this indicates a violation of the thyroid gland – primary hypothyroidism. If the level of TSH is low, this indicates an overactive gland (hyperthyroidism), which produces too many hormones.

Sometimes a low level of thyroid-stimulating hormone is a consequence of a pathology of the pituitary gland, due to which the latter is not able to stimulate the thyroid gland to produce enough hormones. This disorder is called secondary hypothyroidism.

T4 (thyroxine)

An elevated level of thyroxine may indicate hyperthyroidism, and a reduced level may indicate hypothyroidism. In some cases, high or low thyroxine levels are not an indication of a thyroid problem. Pregnant women, as well as those taking oral contraceptives, will have higher T4 levels. Severe illness or taking corticosteroids—drugs used to treat asthma, arthritis, skin conditions, and other conditions—can lower thyroxin levels.

The presence of diseases or medication changes the amount of proteins in the blood that bind to thyroxine. Bound thyroxine is stored in the blood as a reserve and is used only when needed. Free thyroxine does not bind to these proteins and easily penetrates into the tissues of our body. Because changes in bound proteins do not affect free thyroxine levels, many clinicians prefer free T4 testing.

Hormone T3 (triiodothyronine)

If the thyroxin level is normal, but the doctor suspects hyperthyroidism, the patient is given a T3 hormone test to confirm the diagnosis. Sometimes, with normal T4 levels, elevated T3 levels are found. Also, an analysis for free triiodothyronine is prescribed to assess the severity of hyperthyroidism.

Antibody tests

Thyroid antibodies are produced when the immune system mistakenly attacks the thyroid gland. Measuring the level of thyroid antibodies helps to detect autoimmune disorders – Graves’ disease and Hashimoto’s disease.

Antibody tests include:

• Thyroid peroxidase antibodies,
• Thyroglobulin antibodies,
• Thyroid stimulating hormone receptor antibodies.

There is no standard normal range for thyroid antibody tests. This is due to the fact that their level in the blood depends on so many factors.

Other tests

Other specialized tests include tests for:

• Thyroglobulin – prescribed for monitoring patients who have been treated for differentiated thyroid cancer.
• Calcitonin is indicated for monitoring patients with medullary thyroid cancer.

All tests mentioned above are performed in our medical laboratory.

How is thyroid hormone tested?

The patient’s blood sample is obtained from a vein and no special preparation is required for the procedure. Some medications can affect the test result, so if you are taking medication, tell your doctor ahead of time.

What are normal thyroid hormone levels?

Below we will present 2 tables: the first – with normal hormone levels in adults, and the second – with a decoding of the obtained values.

Normal values ​​of thyroid hormones according to British doctors:

057 Norm
Thyrotropic (TSH)	0.4-4 mU/l
Free thyroxine (T4)	9-2 5 pmol/l
Free triiodothyronine (T3)	3. 5-7.8 pmol/l

TSH hormone

T4

T3

9023 5

Interpretation

Increased

Norm

Norm

Mild hypothyroidism

Increased

Decreased

Normal or reduced

Hypothyroidism

Decreased

Normal

Normal

90 228

Mild hyperthyroidism

Decreased

Normal or elevated

Normal or elevated

9 0228

Hyperthyroidism

Reduced or normal

Reduced or normal0003

Non-thyroid related disease; pituitary (secondary) hypothyroidism

Normal

Increased

Increased

9000 2 Hereditary syndrome of resistance to thyroid hormones (reduced tissue sensitivity to hormones)

If you are looking for where take an analysis for thyroid hormones in Kiev, come to the medical center Persomed.