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Lab Work

WHAT IS T4 and T3:


T4 – Thyroxine:


T4 is made by the thyroid or without a thyroid the T4 is obtained through medication such as Synthroid or Levoxyl. T4 by itself has no value. The T4 is converted into T3 as needed for energy.


T4 - Total T4 is the amount of T4 in the blood.


FT4 - Free T4 is the amount of T4 that can be converted into T3. Not all T4 can be converted into T3 which is why most doctors will order the Free T4 lab work.


T3 – Triiodothyronine:


T3 provides the body with energy by taking an atom from T4 and converting it into energy which is then used to regulate such things as the heart rate, blood sugar, body temperature and metabolism.




WHAT IS TSH and THE FUNCTION OF THE PITUITARY GLAND?


Pituitary Gland is known as the "master" endocrine gland under the control of the hypothalamus. The pituitary gland secretes nine hormones one of which is TSH (Thyroid-stimulating hormone).


TSH activates the thyroid to produce T4 and T3. A feedback control system is set up to regulate the amount of thyroid hormones that are in the bloodstream.


Without a thyroid, TSH is still produced to indicate high or low T4/T3 amounts but, obviously without a thyroid, the pituitary gland cannot activate the thyroid to produce those hormones which is why we need thyroid replacement medication.


In the case of Graves, the antibodies cause the thyroid to basically go rogue and produces huge amounts of T4 and T3 which then causes the pituitary gland to stop producing TSH.


  • High amount of T4 and T3 in the blood - the pituitary gland stops the production of TSH.
  • Low amount of T4 and T3 in the blood - the pituitary gland increases production of TSH.
  • Normal TSH and T4 but low T3 could indicate a problem with the body converting T4 into T3


Graves' Disease = Antibodies that active the TSH Receptor (TSH-R)


TSH-R + Antibodies = Thyrotropin Receptor Antibody (TRAb)


The antibodies test TRAb is measured to determine the severity of Graves' Disease and to monitor the success of treatment with medication, radiation or surgery.



UNDERSTANDING LAB WORK:


The standard TSH optimal range is typically 4.5 to 5.0. However, in 2003, the American Association of Clinical Endocrinologists revised these guidelines narrowing the range to .3 to 3.0. Most doctors continue to use the standard range of 4.5 to 5.0.

It's very important to know what optimal range your lab uses when determining the results of your lab work and keep a journal of your lab results.


The lower the TSH number combined with a higher Free T4 & T3 typically points towards Hyperthyroidism.


Free T4 (FT4) - normal range is approximately 0.7 to 2.0

Free T3 (FT3) - normal range is approximately 2.3 to 4.2

Total T4 - Normal Range: 4.5 to 12.5

Total T3 – normal range: 80 to 220



ADDITIONAL LAB WORK TO ASK YOUR DOCTOR


In addition to the routine thyroid lab checks it's really important to discuss the follow additional lab work with your doctor.


  • Comprehensive Vitamin Check (especially Vit D and B12)
  • Lipid Panel or Cholesterol
  • Blood Glucose
  • Blood calcium level test and a bone scan
  • Liver Panel


It's quite common for us with Graves Disease to have low Vit D which can cause a wide range of symptoms similar to what we already experience such as muscle weakness, depression and flu like symptoms. Please see the Vitamins and Nutrition link under the Resource tab for websites relating to vitamins deficiency.