The primary labs taken to monitor the thyroid hormones are TSH, Free T4 and T3.
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.
You do not have to fast for labs, however, I usually have my cholesterol, liver panel and vitamins checked with my thyroid panel so I do fast for labs. I take my thyroid replacement medication once I'm done with labs. Personally, I think it is best to be consistent with lab work. Every six months, I fast in the morning and have labs done no later than 11:30 a.m. I read articles that suggest TSH levels differ between mornings and evenings.
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
Biotin has shown to interfere with lab work. Doctors advise to stop taking biotin two days prior to lab work.
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 Thyroid-stimulating hormone (TSH).
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 causes an increase of T4 and T3. As a result, the pituitary gland to stop producing TSH.
• High amount of T4 & T3 in the blood
- the pituitary gland stops the production of TSH.
• Low amount of T4 & 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.
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 Levothyroxine. T4 by itself has no value. 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 your doctor should order the Free T4 lab work.
T3 – Triiodothyronine:
FT3 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.
Is there additional lab work to consider?
Yes, 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 Vitamins D and B12)
Lipid Panel or Cholesterol
Blood calcium level test and a bone scan
It's quite common for us with Graves' disease to have low vitamin D and B12, which can cause a wide range of symptoms similar to what we already experience such as: muscle weakness, depression and flu like symptoms.
Cholesterol is usually on the low side while in the hyper state, but can significantly increase once the thyroid has been treated.
Monitoring glucose and calcium levels are important to check during active Graves' and at least for the first year after the thyroid is treated.
Liver panel is absolutely necessary if taking ATDs because a large dose has shown to cause liver damage overtime, usually after six months to a year. A low dose of ATDs has been shown safe long-term, but a liver panel should still be done routinely.