Sohel Bhai MBBS

Type 1 and Type 2 Diabetes

Thyroid Function Test (TFT)

Definition

Thyroid Function Test (TFT) is a group of blood tests used to evaluate the function of the thyroid gland. These tests measure the levels of thyroid hormones and Thyroid Stimulating Hormone (TSH) in the blood.

The thyroid gland is located in the neck and produces hormones that regulate metabolism, growth, energy production, body temperature, and heart rate.

TFT helps diagnose thyroid disorders such as hypothyroidism, hyperthyroidism, thyroiditis, and other endocrine abnormalities.

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Principle

The thyroid gland mainly produces:

T3 (Triiodothyronine)

T4 (Thyroxine)

The pituitary gland secretes TSH (Thyroid Stimulating Hormone), which controls thyroid hormone production.

When thyroid hormone levels decrease, the pituitary gland releases more TSH. When thyroid hormone levels increase, TSH secretion decreases.

TFT measures these hormone levels using immunoassay techniques such as:

ELISA

CLIA

ECLIA

These tests help determine whether the thyroid gland is functioning normally.

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Objectives

1. To assess thyroid gland function.

2. To diagnose hypothyroidism and hyperthyroidism.

3. To monitor thyroid hormone therapy.

4. To detect congenital thyroid disorders.

5. To investigate metabolic and hormonal imbalance.

6. To evaluate pituitary-thyroid axis function.

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Specimen

Venous blood sample

Serum (preferred)

Plasma may also be used

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Components of TFT

1. TSH (Thyroid Stimulating Hormone)

Produced by the pituitary gland and regulates thyroid hormone production.

Normal Range

0.4 – 4.0 mIU/L

Increased TSH

Seen in:

Hypothyroidism

Hashimoto thyroiditis

Decreased TSH

Seen in:

Hyperthyroidism

Graves’ disease

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2. T3 (Triiodothyronine)

Active thyroid hormone controlling metabolism.

Normal Range

80 – 200 ng/dL

Increased T3

Hyperthyroidism

Decreased T3

Hypothyroidism

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3. T4 (Thyroxine)

Main hormone produced by thyroid gland.

Normal Range

4.5 – 12.0 µg/dL

Increased T4

Hyperthyroidism

Decreased T4

Hypothyroidism

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4. Free T3 (FT3)

Unbound active form of T3.

Normal Range

2.0 – 4.4 pg/mL

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5. Free T4 (FT4)

Unbound active form of T4.

Normal Range

0.8 – 2.0 ng/dL

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Materials Required

Syringe or vacutainer

Plain blood collection tube

Centrifuge

Immunoassay analyzer

TFT reagent kit

Pipette

Gloves and cotton

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Procedure

1. Collect venous blood sample using aseptic technique.

2. Transfer blood into plain tube.

3. Allow blood to clot.

4. Centrifuge sample to separate serum.

5. Transfer serum into labeled tube.

6. Load serum into analyzer.

7. Add TFT-specific reagents.

8. Analyzer measures hormone levels.

9. Record and interpret results.

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Observation

Increased T3/T4 with decreased TSH indicates hyperthyroidism.

Decreased T3/T4 with increased TSH indicates hypothyroidism.

Normal hormone levels indicate normal thyroid function.

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Clinical Significance

Hypothyroidism

Occurs due to reduced thyroid hormone production.

Causes

Hashimoto thyroiditis

Iodine deficiency

Thyroid surgery

Pituitary disorders

Symptoms

Fatigue

Weight gain

Cold intolerance

Dry skin

Constipation

Slow heartbeat

Depression

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Hyperthyroidism

Occurs due to excessive thyroid hormone production.

Causes

Graves’ disease

Toxic multinodular goiter

Thyroid adenoma

Symptoms

Weight loss

Heat intolerance

Nervousness

Tremors

Sweating

Palpitations

Increased appetite

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Result Interpretation

TFT Findings Interpretation

High TSH + Low T3/T4 Hypothyroidism
Low TSH + High T3/T4 Hyperthyroidism
Normal TSH, T3, T4 Normal thyroid function
High TSH + Normal T4 Subclinical hypothyroidism
Low TSH + Normal T4 Subclinical hyperthyroidism

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Methods Used in TFT

1. ELISA (Enzyme Linked Immunosorbent Assay)

2. CLIA (Chemiluminescent Immunoassay)

3. ECLIA (Electrochemiluminescence Immunoassay)

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Precautions

1. Use properly labeled tubes.

2. Avoid hemolysis of blood sample.

3. Separate serum promptly.

4. Follow analyzer instructions carefully.

5. Store reagents at recommended temperature.

6. Avoid contamination during testing.

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Advantages

Early detection of thyroid disorders

Accurate hormonal evaluation

Useful for treatment monitoring

Helps assess metabolic disorders

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Limitations

Certain drugs may affect results.

Pregnancy can alter thyroid hormone levels.

Severe illness may interfere with TFT values.

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Conclusion

Thyroid Function Test (TFT) is an important hormonal investigation used to assess thyroid gland activity and diagnose thyroid disorders. It plays a major role in evaluating metabolism, endocrine balance, and treatment response in patients with thyroid disease.

Important Sign Must Know All Medical Student

🎯APGAR Score

DNA Test
Definition
DNA Test (Deoxyribonucleic Acid Test) is a laboratory test used to analyze genetic material present in cells. It helps identify genetic relationships, inherited diseases, mutations, and individual identity.
DNA testing is widely used in medical diagnosis, forensic science, paternity testing, and genetic research.
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Principle
DNA is extracted from biological samples such as blood, saliva, or hair. Specific DNA regions are amplified using techniques like Polymerase Chain Reaction (PCR) and analyzed to detect genetic variations or matching patterns.
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Objectives
1. To identify genetic disorders.
2. To determine biological relationships.
3. To detect inherited mutations.
4. To assist forensic investigations.
5. To study genetic characteristics.
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Specimen
• Blood sample
• Saliva or buccal swab
• Hair root
• Semen or tissue sample
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Normal Findings
• Normal DNA pattern without mutation
• Genetic markers match expected profile
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Common Types of DNA Tests
1. Paternity DNA Test
2. Genetic Disease Testing
3. Forensic DNA Profiling
4. Prenatal Genetic Testing
5. Ancestry DNA Testing
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Materials Required
• Sterile swab or syringe
• Sample collection tube
• DNA extraction kit
• PCR machine
• Micropipette
• Gel electrophoresis apparatus
• DNA analyzer
• Gloves and laboratory reagents
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Procedure
1. Collect biological sample using sterile technique.
2. Extract DNA from the sample.
3. Purify the extracted DNA.
4. Amplify target DNA using PCR.
5. Separate DNA fragments by gel electrophoresis or analyzer.
6. Analyze DNA patterns and genetic markers.
7. Record and interpret results.
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Observation
• DNA bands or peaks are observed after analysis.
• Matching DNA patterns indicate biological relationship or identity.
• Mutations may indicate genetic disorders.
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Clinical Significance
Medical Uses
• Detection of genetic diseases
• Cancer mutation analysis
• Prenatal diagnosis
Forensic Uses
• Criminal identification
• Crime scene investigation
Relationship Testing
• Paternity and maternity confirmation
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Precautions
1. Use sterile equipment to avoid contamination.
2. Label samples correctly.
3. Store samples properly.
4. Handle reagents carefully.
5. Follow laboratory biosafety rules.
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Result Interpretation
DNA Result Interpretation
Matching DNA profile Biological relationship/identity confirmed
Non-matching profile Relationship excluded
Mutation detected Possible genetic disorder
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Advantages
• Highly accurate
• Reliable identification method
• Early detection of inherited diseases
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Limitations
• Expensive in some cases
• Requires specialized laboratory equipment
• Risk of contamination if improperly handled
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Conclusion
DNA testing is an advanced molecular laboratory investigation used for genetic analysis, disease diagnosis, forensic identification, and relationship testing. It plays a major role in modern medicine, biotechnology, and criminal investigation.

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