HealthFlex
×
  • Home
  • Immunology Book
  • Lab Tests
    • Hematology
    • Fluid analysis
    • CSF
    • Urine Analysis
    • Chemical pathology
    • Blood banking
    • Fungi
    • General pathology
    • Immune system
    • Microbiology
    • Parasitology
    • Pathology
    • Tumor marker
    • Virology
    • Cytology
  • Lectures
    • Bacteriology
    • Liver
    • Lymph node
    • Mycology
    • Virology
  • Blog
    • Economics and technical
    • Fitness health
    • Mental health
    • Nutrition
    • Travel
    • Preventive health
    • Nature and photos
    • General topic
  • Medical Dictionary
  • About Us
  • Contact

Thyroid – Part 5 – Thyroxine Total, T4 Total

September 28, 2020Chemical pathologyLab Tests

Sample

  1. This test is done on the serum of the patient.
  2. The sample is stable for 7 days at room temperature but refrigeration at 4 °C is preferred.

Precaution

  • Avoid lipemic serum.

Indications

  1. This is done to assess thyroid function.
  2. it is done to diagnose thyroid diseases.
  3. This is also done to monitor the therapy.

Pathophysiology

  1. Thyroxine T4 forms by the combination of :
    1. diiodotyrosine + diiodotyrosine = Tetra Iodo Tyrosine (Thyroxine or T4).
Thyroid hormone synthesis

Thyroid hormone synthesis

  1. T4 makes most of the thyroid hormone because T3 is 10 %.
    1. 80% of the T4 is metabolized into:
      1. T3 = 35%
      2. rT3 = 45%
  2. Most of the T4 is bound to thyroglobulin and albumin.
    1. T4  is pro-hormone with thyroglobulin binding (TBG).
Carrier proteins for thyroxine

Carrier proteins for thyroxine

  1. There is a very small fraction of free T4.
    1. Serum Total T4 = bound T4 + Free T4
Thyroid hormone metabolism

Thyroid hormone metabolism

  1. Thyroid glands have a major role in body function. T4 and T3 have a role in the growth, maturation of bone, and skeletal system.
    1. T3 is 3 to 8 times more metabolically active than T4 and is considered the active form of the thyroid hormone.
    2. It regulates body temperature.
    3. It has a role in the body’s metabolism of fats, carbohydrates, and proteins.
Functions of the thyroid hormone

Functions of the thyroid hormone

Increased thyroid hormone effect on the body

Increased thyroid hormone effect on the body

NORMAL

Source 1

T4 Total (T4)

Age µg/dL
Cord blood 7.4 to 13.0
1 to 3 days 11.8 to 22.6
1 to 2 weeks 9.8 to 16.6
1 to 4 month 7.2 to 14.4
4 to 12 month 7.8 to 16.5
1 to 5 year 7.3 to 15.0
5 to 10 year 6.4 to 13.3
10 to 15 year 5.6 to 11.7
Adult  Male =  4.6 to 10.5           Female  =   5.5 to 11.0
>60 year 5.0 to 10.7
Maternal serum 15 to 40 weeks 9.1 to 14.0
Source 1

T4 Free (FT4)

 Age  ng/dL
 Newborn 1 to 4 days  2.2 to 5.3
 Child (2 weeks to 20 Years  0.8 to 2.0
 Adult 21 to 87 years 0.8 to 2.7
 Pregnancy
1st trimester  0.7 to 2.0
 2nd and 3rd trimester 0.5 to 1.6
  • To converts SI unit x 12.9 = nmol/L

Source 2

T4 Total (T4)

Age µg/dL
1 to 3 days 11.22
1 to 2 weeks 10 to 16
1 o 12 months 8 to 16
1 to 5 years 7 to 15
5to 10 years 6 to 13
10 to 15 years 5 to 12
Adult Male 4 to 12      Female 5 to 12
>60 years  5 to 11
Source 2

T4 Free

  • Newborn (0 to 4 days) = 2 to 6 ng/dL  (26 to 77 pmol/L)
  • Child 2 weeks to 20 years = 0.8 to 2.0 ng//dL
  • Adult  = 0.8 to 2.8 ng/dL (10 to 36 pmol/L)
  • Infants 1 to 3 days = 11 to 22  µg/dL.
    • Infants 1 to 4 months = 8 to 16 .µg/dL
  • Child 1 to 5 years = 7 to 15 .µg/dL
    • Child 10 to 15 years = 5 to 12 µg/dL.
  • Adult Male = 4 to 12  µg/dL.
    • Adult female = 5 to 12 µg/dL.
    • adult > 60 years = 5 to 11 µg/dL.

The increased T4 level is seen in:

  1. Grave’s disease.
  2. Toxic thyroid adenoma.
  3. Struma ovarii.
  4. Acute thyroiditis.

The decreased T4 level is seen in:

  1. Hypothyroidism like:
    1. Cretinism.
    2. Myxedema.
    3. Surgical ablation.
  2. Failure of the hypothalamus.
  3. Protein-losing conditions like :
    1. Nephrotic syndrome.
    2. Renal failure.
  4. Iodine insufficiency.
  5. Cirrhosis.
  6. Cushing’s syndrome.
  7. Advanced cancers.
  8. Pituitary insufficiency.

The critical value of T4 Total:

  • Newborn = <7 µg/dL
  • Adult = <2 µg/dL

Please see more details in Free T4 and thyroid function.


Possible References Used
Go Back to Chemical pathology

Add Comment Cancel


  • Lab Tests
    • Blood banking
    • Chemical pathology
    • CSF
    • Cytology
    • Fluid analysis
    • Fungi
    • General pathology
    • Hematology
    • Immune system
    • Microbiology
    • Parasitology
    • Pathology
    • Tumor marker
    • Urine Analysis
    • Virology

About Us

Labpedia.net is non-profit health information resource. All informations are useful for doctors, lab technicians, nurses, and paramedical staff. All the tests include details about the sampling, normal values, precautions, pathophysiology, and interpretation.

[email protected]

Quick Links

  • Blog
  • About Us
  • Contact
  • Disclaimer

Our Team

Professor Dr. Riaz Ahmad Bhutta

Dr. Naheed Afroz Syed

Dr. Asad Ahmad, M.D.

Dr. Shehpar Khan, M.D.

Copyright © 2014 - 2022. All Rights Reserved.
Web development by Farhan Ahmad.