What is the collective term for blood tests used to assess thyroid function?

The collective term for blood tests used to check the function of the thyroid gland is Thyroid Function Tests (TFTs).

Under what circumstances might a doctor request thyroid function tests?

Thyroid function tests may be requested if a patient is suspected of having hyperthyroidism (an overactive thyroid) or hypothyroidism (an underactive thyroid). They are also used to monitor the effectiveness of treatments for these conditions, such as thyroid-suppression or hormone replacement therapy. Additionally, TFTs are sometimes ordered routinely for patients with conditions linked to thyroid disease, like atrial fibrillation or anxiety disorder.

How does thyroid-stimulating hormone (TSH) levels typically relate to thyroid function?

Thyroid-stimulating hormone (TSH) levels are generally elevated in cases of hypothyroidism (underactive thyroid) and decreased in cases of hyperthyroidism (overactive thyroid). This makes TSH a crucial test for the early detection of both conditions.

What is the significance of TSH in diagnosing thyroid conditions?

TSH is considered the most important test for the early detection of both hypothyroidism and hyperthyroidism. An elevated TSH level typically suggests hypothyroidism, while a low TSH level generally indicates hyperthyroidism. However, measuring TSH alone can sometimes be misleading, necessitating comparison with other thyroid function tests for an accurate diagnosis.

Where is TSH produced, and what controls its production?

Thyroid-stimulating hormone (TSH) is produced in the pituitary gland. Its production is regulated by thyrotropin-releasing hormone (TRH), which is synthesized in the hypothalamus. High levels of free T3 or free T4 in the blood can suppress TSH levels.

When were the first-generation TSH assays introduced, and what method did they use?

The first-generation TSH assays were introduced in 1965 and utilized radioimmunoassay (RIA) techniques.

How did TSH assay technology evolve after the initial radioimmunoassay methods?

While variations and improvements were made to TSH radioimmunoassays, their use declined with the advent of a new immunometric assay technique in the mid-1980s. Subsequent generations of TSH assays (second, third, and fourth) offered increased accuracy, with each generation demonstrating a tenfold increase in functional sensitivity compared to the previous one.

What is considered the modern standard for TSH testing?

The third-generation TSH assay is considered the requirement for modern standards of care in TSH testing. In the United States, these tests are typically performed using automated platforms that employ advanced immunometric assay methods.

Is there a universally accepted international standard for measuring TSH?

No, there is currently no international standard for the measurement of thyroid-stimulating hormone (TSH).

What factors must be considered for the accurate interpretation of thyroid function tests?

Accurate interpretation of thyroid function tests requires considering various factors. These include the levels of thyroid hormones like thyroxine (T4) and triiodothyronine (T3), the patient's current medical status (such as pregnancy), the use of certain medications (like propylthiouracil), temporal effects like circadian rhythm and hysteresis, and the patient's overall medical history.

How can pregnancy affect total thyroxine levels?

During pregnancy, total thyroxine (Total T4) levels are usually slightly elevated. This increase is secondary to higher levels of thyroid-binding globulin (TBG) in the blood.

Why is total T3 sometimes preferred over total T4 in clinical practice?

Total triiodothyronine (Total T3) is sometimes measured in clinical practice because a smaller proportion of T3 is bound to proteins compared to T4. This makes Total T3 potentially more informative than Total T4, especially when protein binding abnormalities might be present.

What are the typical reference ranges for total thyroxine (Total T4)?

Reference ranges for Total T4 vary by laboratory method. Example values indicate a lower limit of 4.0 or 5.5 µg/dL and an upper limit of 11.0 or 12.3 µg/dL, which corresponds to 60 to 140 nmol/L.

What does free thyroxine (fT4) indicate in thyroid function tests?

Free thyroxine (fT4) levels are generally elevated in hyperthyroidism and decreased in hypothyroidism. It represents the unbound, biologically active form of thyroxine.

What are the typical reference ranges for free thyroxine (fT4) in normal adults?

For normal adults, the typical reference range for free thyroxine (fT4) is between 0.7 to 1.4 ng/dL or 0.8 to 1.5 ng/dL. In molar concentration, this is approximately 9 to 18 pmol/L or 10 to 23 pmol/L. It's important to note that reference ranges can differ based on the specific laboratory analysis method used.

How do free thyroxine (fT4) levels differ in infants compared to adults?

Free thyroxine (fT4) levels are higher in newborns. For infants aged 0-3 days, the range is typically 2.0 to 5.0 ng/dL (26 to 65 pmol/L). For infants aged 3-30 days, the range is 0.9 to 2.2 ng/dL (12 to 30 pmol/L). These levels decrease with age, approaching adult ranges by adolescence.

What is the typical interpretation of total triiodothyronine (Total T3) levels in thyroid disorders?

Similar to Total T4, Total triiodothyronine (Total T3) levels are generally elevated in hyperthyroidism and decreased in hypothyroidism. However, like Total T4, it is rarely measured now, having been largely superseded by free T3 tests.

What are the typical reference ranges for total triiodothyronine (Total T3) in adults?

Typical reference ranges for total triiodothyronine (Total T3) in adults are approximately 60 to 175 ng/dL or 75 to 181 ng/dL. In molar concentration, this is about 0.9 to 2.5 nmol/L or 1.1 to 2.7 nmol/L, though these values can vary by laboratory.

What does free triiodothyronine (fT3) indicate, and how does it change in thyroid dysfunction?

Free triiodothyronine (fT3) levels are generally elevated in hyperthyroidism and decreased in hypothyroidism. It represents the unbound, active form of triiodothyronine, which is a key thyroid hormone.

What are the reference ranges for free triiodothyronine (fT3) in normal adults?

For normal adults, the typical reference range for free triiodothyronine (fT3) is between 3.0 to 7.0 pg/mL or 3.1 to 7.7 pg/mL. In picomoles per liter, this is approximately 4.6 to 10.8 pmol/L or 4.8 to 11.8 pmol/L, depending on the laboratory's assay.

How does thyroxine-binding globulin (TBG) influence total thyroid hormone levels?

An increase in thyroxine-binding globulin (TBG) leads to an elevation in total thyroxine (Total T4) and total triiodothyronine (Total T3) levels. Importantly, this increase in total hormones does not reflect an actual increase in the body's hormonal activity, as the free, active hormone levels remain unchanged.

What is measured by the thyroid hormone uptake test (T3 uptake)?

The thyroid hormone uptake test, also known as T3 uptake, measures the amount of unsaturated thyroxine-binding globulins (TBG) in the blood. It indicates the capacity of TBG to bind thyroid hormones and is not directly related to triiodothyronine levels, despite its name.

How do thyroid hormone uptake levels change with thyroid hormone levels?

Unsaturated TBG levels increase when there are decreased levels of thyroid hormones in the blood. Conversely, when thyroid hormone levels are high, more TBG is saturated, leading to lower T3 uptake readings.

What is the Free Thyroxine Index (FTI or T7), and why was it developed?

The Free Thyroxine Index (FTI), also known as T7, is calculated by multiplying the total thyroxine (Total T4) level by the T3 uptake value. It was developed as a more reliable indicator of thyroid status, particularly when abnormalities in plasma protein binding might affect the accuracy of total T4 measurements alone.

Is the Free Thyroxine Index (FTI) still commonly used in thyroid testing?

No, the Free Thyroxine Index (FTI) is rarely used today because reliable assays for free thyroxine (fT4) and free triiodothyronine (fT3) are now routinely available and provide more direct measures of active thyroid hormones.

What are derived structure parameters in thyroid function testing, and what is their purpose?

Derived structure parameters, such as SPINA-GT and SPINA-GD, are calculated values that describe constant properties of the thyroid-pituitary feedback control system. They can provide additional information for specific diagnostic purposes, such as in cases of nonthyroidal illness syndrome or central hypothyroidism.

What does Thyroid's Secretory Capacity (SPINA-GT) represent?

Thyroid's Secretory Capacity (SPINA-GT) represents the maximum amount of thyroxine the thyroid gland can produce in one second when stimulated. This value is elevated in hyperthyroidism and reduced in hypothyroidism.

What is Jostel's TSH index (JTI or TSHI), and what does it help determine?

Jostel's TSH index (JTI or TSHI) is a calculated parameter used to quantitatively assess the thyrotropic function of the anterior pituitary gland. It is often reduced in cases of thyrotropic insufficiency and certain types of nonthyroidal illness syndrome.

How is Jostel's TSH index (TSHI) calculated?

Jostel's TSH index (TSHI) is calculated using the formula: TSHI = LN(TSH) + 0.1345 * FT4, where LN is the natural logarithm, TSH is thyroid-stimulating hormone, and FT4 is free thyroxine.

What is the standardized form of the TSH index, and how is it calculated?

A standardized form of the TSH index, known as sTSHI, can be calculated using the formula: sTSHI = (TSHI - 2.7) / 0.676. This standardization helps in comparing results across different studies or populations.

What is the Thyrotroph Thyroid Hormone Sensitivity Index (TTSI), and what is its primary use?

The Thyrotroph Thyroid Hormone Sensitivity Index (TTSI), also referred to as the Thyrotroph T4 Resistance Index (TT4RI), was developed as a tool for rapidly screening patients for resistance to thyroid hormone. It is calculated using equilibrium values of TSH and FT4, employing a different equation than the TSH Index.

What is the Thyroid Feedback Quantile-based Index (TFQI), and what does it measure?

The Thyroid Feedback Quantile-based Index (TFQI) is another parameter used to evaluate thyrotropic pituitary function. It is designed to be more robust against data distortions than other indices like JTI and TTSI. TFQI is calculated using the quantiles of FT4 and TSH concentrations.

What are the typical associations with higher TFQI values?

Higher TFQI values have been associated with conditions such as obesity, metabolic syndrome, impaired kidney function, diabetes, and increased diabetes-related mortality. It may also be elevated in takotsubo syndrome, potentially indicating increased allostatic load due to psychosocial stress.

How can drugs affect thyroid function test results?

Drugs can significantly alter thyroid function test results. For example, dopamine, glucocorticoids, and somatostatin can inhibit TSH secretion, leading to decreased T4 and T3 levels. Conversely, drugs like iodine and lithium can inhibit thyroid hormone synthesis or release, causing decreased T4 and T3 but increased TSH.

Which drugs can inhibit the conversion of T4 to T3 and what are their effects on TFTs?

Drugs such as amiodarone, glucocorticoids, propranolol, propylthiouracil, and radiographic contrast agents can inhibit the conversion of T4 to T3. This typically results in decreased T3, increased reverse T3 (rT3), variable effects on T4 and fT4, and unchanged or increased TSH. These drugs can also lead to a decrease in the SPINA-GD parameter.

What types of drugs can inhibit the binding of thyroid hormones to serum proteins, and what are the observed effects?

Drugs like salicylates, phenytoin, carbamazepine, furosemide, nonsteroidal anti-inflammatory agents, and heparin (in vitro) can inhibit the binding of thyroid hormones to serum proteins. This can lead to decreased total T4 and T3, decreased free T4 index (fT4E), variable or increased free T4 (fT4), unchanged TSH, and a decrease in the T4/fT4 ratio.

What are the effects of drugs that increase the concentration of T4-binding proteins on thyroid function tests?

Drugs such as estrogen, clofibrate, and certain opiates (heroin, methadone) can increase the concentration of T4-binding proteins. This typically results in increased total T4 and T3, unchanged free T4, and unchanged TSH. It can also lead to an increase in the T4/fT4 ratio and no change in SPINA-GT or SPINA-GD.

What are the effects of drugs that decrease the concentration of T4-binding proteins on thyroid function tests?

Androgens and glucocorticoids can decrease the concentration of T4-binding proteins. This typically leads to decreased total T4 and T3, unchanged free T4, and unchanged TSH. It also results in a decrease in the T4/fT4 ratio.

Which drugs can inhibit the absorption of ingested thyroxine (T4) and what are their effects?

Several substances can inhibit the absorption of ingested T4, including aluminum hydroxide, ferrous sulfate, cholestyramine, colestipol, iron sucralfate, soybean preparations, and Kayexalate. These can lead to decreased T4 and fT4 levels, and consequently, an increase in TSH.

What is the purpose of the CDC laboratory procedure manuals mentioned in relation to TSH testing?

The Centers for Disease Control and Prevention (CDC) publishes laboratory procedure manuals that detail the methods used for measuring thyroid-stimulating hormone (TSH). These manuals, often specifying methods like Access 2 (Beckman Coulter) or Microparticle Enzyme Immunoassay, ensure standardization and accuracy in TSH testing.

What does the reference range for thyroglobulin typically indicate?

The reference ranges for thyroglobulin are provided, typically measured in pmol/L or µg/L. Thyroglobulin is a protein produced by the thyroid gland and is often used as a tumor marker for differentiated thyroid cancer.

What is the significance of the T4/fT4 ratio in thyroid function testing?

The T4/fT4 ratio can be affected by drugs that alter the binding of T4 to serum proteins. An increase in this ratio might be seen with drugs that increase T4-binding proteins (like estrogen), while a decrease might occur with drugs that inhibit binding (like salicylates or phenytoin).

What is the role of Transthyretin (prealbumin) and Albumin in thyroid hormone transport?

Transthyretin (also known as prealbumin) and Albumin are other binding proteins in the blood that transport thyroid hormones. While TBG is the primary carrier, changes in the levels of these proteins can also influence total thyroid hormone concentrations.

What is the primary purpose of the SPINA-GT parameter?

SPINA-GT, or Thyroid's Secretory Capacity, is a calculated parameter used to assess the maximum stimulated output of thyroxine from the thyroid gland. It helps in differentiating between various thyroid conditions by quantifying the thyroid's functional capacity.

What does the SPINA-GD parameter represent?

SPINA-GD, representing the sum activity of peripheral deiodinases, is a calculated parameter that reflects the body's ability to convert thyroid hormones. It is particularly useful in identifying conditions like nonthyroidal illness syndrome, where this conversion process may be impaired.

What is the clinical relevance of the TFQI parameter?

The TFQI (Thyroid Feedback Quantile-based Index) is a robust parameter for assessing thyrotropic pituitary function. Its values are associated with various metabolic and health conditions, including obesity, diabetes, and renal function, potentially reflecting overall allostatic load or stress responses.

How is the concept of a 'set point' applied to thyroid homeostasis?

In healthy individuals, thyroid hormone levels tend to remain relatively stable within a narrow range due to a personal 'set point' for thyroid homeostasis. This set point represents the individual's unique target level for thyroid function, and deviations from it can indicate thyroid dysfunction. Methods exist to reconstruct this personal set point.

What is the significance of narrow individual variations in thyroid hormone levels?

The observation of narrow individual variations in thyroid hormone levels, compared to the wider inter-individual variations, suggests the existence of a personal set point for thyroid homeostasis. This concept is important for understanding subclinical thyroid disease and tailoring treatment.

Thyroid Function Tests Wiki: Thyroid Diagnostics Unveiled: A Comprehensive Analysis of Function Tests

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Introduction to TFTs

Purpose of TFTs

Thyroid Function Tests (TFTs) encompass a suite of blood tests designed to evaluate the operational status of the thyroid gland. These assays are pivotal when investigating potential thyroid dysfunction, specifically hyperthyroidism (an overactive thyroid) or hypothyroidism (an underactive thyroid). They are also instrumental in monitoring the efficacy of therapeutic interventions, whether thyroid hormone suppression or replacement therapy.

Clinical Applications

Beyond direct thyroid assessment, TFTs are frequently ordered in patients presenting with conditions often associated with thyroid disease. This includes, but is not limited to, atrial fibrillation and anxiety disorders, where thyroid status can significantly influence or exacerbate symptoms. Routine monitoring in specific patient populations also necessitates TFTs.

Core Analytes

A standard TFT panel typically quantifies key thyroid hormones circulating in the blood. The primary analytes usually include Thyroid-Stimulating Hormone (TSH), also known as thyrotropin, and Thyroxine (T4). Depending on the specific laboratory's protocols and the clinical context, Triiodothyronine (T3) levels may also be included in the panel.

Thyroid-Stimulating Hormone (TSH)

TSH: The Primary Indicator

Thyroid-Stimulating Hormone (TSH), secreted by the pituitary gland, is the most sensitive indicator for the initial detection of both hypothyroidism and hyperthyroidism. Elevated TSH levels typically suggest hypothyroidism, while suppressed TSH levels generally point towards hyperthyroidism. Its production is regulated by Thyrotropin-Releasing Hormone (TRH) from the hypothalamus.

Interpretation Nuances

While TSH is a crucial marker, interpreting it in isolation can sometimes yield misleading results. Accurate diagnosis necessitates correlating TSH values with other thyroid function tests, such as free T4 and free T3. Factors like pregnancy, certain medications (e.g., propylthiouracil), and physiological rhythms can influence TSH levels, requiring careful clinical consideration.

Historical Context

The evolution of TSH assays began with radioimmunoassays in 1965. Significant advancements led to immunometric assays in the mid-1980s, offering improved accuracy and sensitivity. Subsequent generations (second, third, and fourth) have progressively enhanced functional sensitivity, with third-generation assays representing the current standard of care, often automated for efficiency.

Thyroid Hormones: T4 and T3

Total Thyroxine (Total T4)

Total T4 measurement, reflecting both bound and unbound thyroxine, is less commonly used now, largely superseded by free T4 assays. Elevated levels are seen in hyperthyroidism, and decreased levels in hypothyroidism. Pregnancy typically causes a slight elevation due to increased Thyroid Binding Globulin (TBG).

Example Reference Ranges (vary by lab):

Lower Limit	Upper Limit	Unit
4.0	11.0	µg/dL
60	140	nmol/L

Free Thyroxine (fT4)

Free Thyroxine (fT4) represents the unbound, biologically active fraction of T4. It is a more reliable indicator of thyroid status than total T4, especially when protein binding abnormalities are suspected. Levels are elevated in hyperthyroidism and decreased in hypothyroidism. Reference ranges vary significantly based on assay methodology.

Example Reference Ranges (vary by lab):

Patient Type	Lower Limit	Upper Limit	Unit
Normal Adult	0.8	1.8	ng/dL
Normal Adult	10	23	pmol/L

Total and Free Triiodothyronine (T3)

Similar to T4, total T3 is less frequently measured than free T3 (fT3). Both total and free T3 levels are generally elevated in hyperthyroidism and decreased in hypothyroidism. T3 assays are sometimes preferred due to a smaller fraction being protein-bound compared to T4.

Example Reference Ranges (Total T3, vary by lab):

Test	Lower Limit	Upper Limit	Unit
Total Triiodothyronine	75	181	nmol/L

Carrier Proteins

Thyroxine-Binding Globulin (TBG)

TBG is the primary protein responsible for binding thyroid hormones in the blood. Elevated TBG levels, seen in conditions like pregnancy or estrogen therapy, can increase total T4 and T3 concentrations without altering the actual thyroid hormone activity or free hormone levels. Conversely, decreased TBG can lower total hormone levels.

Example Reference Ranges (TBG, vary by lab):

Lower Limit	Upper Limit	Unit
12	30	mg/L

Thyroglobulin (Tg)

Thyroglobulin is a protein produced by thyroid follicular cells. While not a direct measure of thyroid function (hormone levels), Tg levels are primarily used as a tumor marker in the management of differentiated thyroid cancer (papillary and follicular). Elevated levels post-thyroidectomy can indicate residual or recurrent disease.

Example Reference Ranges (Tg, vary by lab):

Lower Limit	Upper Limit	Unit
1.5	30	pmol/L
1	20	µg/L

Calculated Parameters

Free Thyroxine Index (FTI)

The FTI, calculated by multiplying total T4 by the T3 uptake ratio, was historically used to estimate free thyroxine levels, especially when protein binding was abnormal. It is now largely replaced by direct free hormone assays but provides insight into the interplay between hormone levels and binding capacity.

Example Reference Ranges (FTI, vary by lab):

Patient Type	Lower Limit	Upper Limit
Females	1.8	5.0
Males	1.3	4.2

Advanced Indices (SPINA, JTI, TTSI, TFQI)

More sophisticated parameters derived from systems theory offer deeper insights into thyroid homeostasis. These include:

SPINA-GT (Secretory Capacity): Assesses the thyroid's maximum stimulated hormone production capacity.
SPINA-GD (Deiodinase Activity): Reflects the activity of peripheral enzymes converting T4 to T3.
Jostel's TSH Index (JTI): Quantifies the pituitary's thyrotropic function.
Thyrotroph Thyroid Hormone Sensitivity Index (TTSI): Another measure of pituitary sensitivity to thyroid hormones.
Thyroid Feedback Quantile-based Index (TFQI): A robust parameter assessing thyrotropic pituitary function, correlating with metabolic health factors.

These indices are valuable in complex cases, such as non-thyroidal illness syndrome or central hypothyroidism, aiding in more precise diagnosis and management strategies.

Pharmacological Influences

Drug Effects on TFTs

Numerous medications can significantly alter thyroid function test results, mimicking or masking thyroid dysfunction. Understanding these interactions is critical for accurate interpretation. Key mechanisms include interference with TSH secretion, hormone synthesis, peripheral conversion, and protein binding.

Examples:

Dopamine, Glucocorticoids: Can suppress TSH, T4, and T3 levels.
Amiodarone, Propranolol: Inhibit T4 to T3 conversion, affecting T3 levels and potentially TSH.
Estrogens: Increase TBG, leading to higher total T4/T3 but typically normal free T4/T3 and TSH.
Phenytoin, Phenobarbital: Can induce hepatic enzymes, increasing hormone metabolism and potentially lowering T4/T3.
Iron, Calcium, Antacids: Can impair T4 absorption, leading to elevated TSH.

Effects of Selected Drugs on Thyroid Function Tests
Mechanism	Drug Examples	Effect on Hormones (T4/T3)	Effect on TSH	Effect on Indices
Inhibited TSH Secretion	Dopamine, Glucocorticoids, Somatostatin	↓ T4, ↓ T3	↓ TSH	↓ JTI
Inhibited Synthesis/Release	Iodine, Lithium	↓ T4, ↓ T3	↑ TSH	↓ SPINA-GT
Inhibited T4 → T3 Conversion	Amiodarone, Propranolol, Propylthiouracil	↓ T3, variable T4	↔ or ↑ TSH	↓ SPINA-GD
Inhibited Hormone Binding	Salicylates, Phenytoin, Furosemide	↓ Total T4, variable fT4	↔ TSH	↓ T4/fT4 ratio
Increased Binding Protein Concentration	Estrogens, Clofibrate	↑ Total T4, ↑ Total T3	↔ TSH	↑ T4/fT4 ratio
Decreased Binding Protein Concentration	Androgens, Glucocorticoids	↓ Total T4, ↓ Total T3	↔ TSH	↓ T4/fT4 ratio
Impaired T4 Absorption	Iron, Calcium, Antacids	↓ T4	↑ TSH	N/A

(Note: Effects can be complex and vary based on dosage and individual response.)

Related Information

Reference Ranges

Understanding thyroid function necessitates comparing patient results against established reference ranges. These ranges are critical for diagnosis but can vary based on laboratory methodology, patient demographics (age, sex, pregnancy status), and assay standardization. Always refer to the specific laboratory's provided ranges for accurate interpretation.

Further Resources

For deeper insights into thyroid physiology, diagnostics, and treatment, consult authoritative sources:

American Thyroid Association: Provides patient and professional resources on thyroid health.
Lab Tests Online: Offers detailed explanations of various laboratory tests, including thyroid panels.
SPINA Thyr Software: Open-source tools for calculating advanced thyroid homeostasis parameters.

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References

Reference range list from Uppsala University Hospital ("Laborationslista"). Artnr 40284 Sj74a. Issued on April 22, 2008

A full list of references for this article are available at the Thyroid function tests Wikipedia page

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This content has been generated by an AI model and is intended solely for educational and informational purposes. It is based on data extracted from Wikipedia and may not reflect the most current medical knowledge or practices. The information provided is not a substitute for professional medical advice, diagnosis, or treatment.

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Thyroid Diagnostics Unveiled

💡 Dive in with Flashcard Learning! 💡

Introduction to TFTs 🧪

📊 Purpose of TFTs

🩺 Clinical Applications

🔬 Core Analytes

Thyroid-Stimulating Hormone (TSH) ⬆️

⚙️ TSH: The Primary Indicator

⚠️ Interpretation Nuances

📜 Historical Context

Thyroid Hormones: T4 and T3 🌡️

📉 Total Thyroxine (Total T4)

📈 Free Thyroxine (fT4)

🔄 Total and Free Triiodothyronine (T3)

Carrier Proteins 🔗

🌐 Thyroxine-Binding Globulin (TBG)

🧬 Thyroglobulin (Tg)

Calculated Parameters 🧮

💡 Free Thyroxine Index (FTI)

📈 Advanced Indices (SPINA, JTI, TTSI, TFQI)

Pharmacological Influences 💊

薬 Drug Effects on TFTs

Related Information 📚

⚖️ Reference Ranges

🔗 Further Resources

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Disclaimer ⚠️

📜 Important Notice

Dive in with Flashcard Learning!

Introduction to TFTs

Purpose of TFTs

Clinical Applications

Core Analytes

Thyroid-Stimulating Hormone (TSH)

TSH: The Primary Indicator

Interpretation Nuances

Historical Context

Thyroid Hormones: T4 and T3

Total Thyroxine (Total T4)

Free Thyroxine (fT4)

Total and Free Triiodothyronine (T3)

Carrier Proteins

Thyroxine-Binding Globulin (TBG)

Thyroglobulin (Tg)

Calculated Parameters

Free Thyroxine Index (FTI)

Advanced Indices (SPINA, JTI, TTSI, TFQI)

Pharmacological Influences

Drug Effects on TFTs

Related Information

Reference Ranges

Further Resources

Teacher's Corner

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Test Your Knowledge!

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Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice