"A study of euthyroid adult population was undertaken to determine expected values for the Free T4 EIA Test System. The mean (X) values, standard deviations (σ) and expected ranges (±2 σ) are presented in Table 1.
Expected Values for the Free T4 EIA Test System
Adult (89 specimens)
Mean (X) 1.40
Standard Deviation (σ) 0.30
Expected Ranges (±2 σ) 0.8 – 2.0
Pregnancy (3 Ispecimens)
Mean (X) 1.50
Standard Deviation (σ) 0.37
Expected Ranges (±2 σ) 0.76 – 2.24"
Excerpt from Diagnostic Automation Inc - Free T4 ELISA kit
"A study of euthyroid adult population was undertaken to determine expected values for the FT3 DAI ELISA test system. The mean values (X), standards deviations (σ) and expected ranges (±2σ.) are presented in Table 1
Expected Values for the Free T3 ELISA Test System
Adult (110 speciments)
Mean (X) 2.8
Standard Deviation (σ) 0.7
Expected Ranges (±2 σ) 1.4 - 4.2
Pregnancy (75 specimens)
Mean (X) 3.0
Standard Deviation (σ) 0.6
Expected Ranges (±2 σ) 1.8 - 4.2"
Excerpt from Diagnostic Automation Inc - Free T3 ELISA
"When we have a normal population data for serum TSH we need to log-tranform the values in order to get the familiar bell-shaped curve that defines a normal distribution. The normal range is usually quoted as about 0.4 - 4mU/L (millunits per litre), but the log transformation introduces one peculiarity - it move the mean and median values for TSH down towards the lower end of the range - at about 1mU/L.
The upwards tail between 2 and 4mU/L is rather thin, and there is room for doubt as to whether values in this range are actually normal or not. The important point is that when normalizing TSH by treatment, our target (the mean and median) TSH value should generally be around 1mU/L. If we simply aim for TSH in the middle of the range, some individuals will remain under-treated."
- Prof Jim Stockigt. "Subclinical hypothyroidism or Mild thyroid failure: How important is early diagnosis and what treatment is optimal? Sigma Pharmaceuticals, March 2001. [Thyroid Australia, Thyroid flyer. 2:3, July 2001.]
Thyroid levels in people who do not have a thyroid condition, have hormones "on demand", meaning that their thyroid produces, or they convert, to produce adequate hormones, as needed, which fluctuates throughout the day.
Those of us who have a thyroid condition and are on replacement medication, do not have the hormones on demand and must rely on adequate dosage/conversion in order to keep our levels where we need them.
It's already been shown that people with undiagnosed thyroid conditions, help make up the basis for the so-called "normal" ranges, which causes them to be flawed. The AACE recommended that the TSH range be adjusted to take this into consideration, but most labs, and therefore, doctors, don't go by the new range (0.3-3.0), which leaves many people with TSH above 3.0, undiagnosed. Likewise, many people with lower levels of FT3 and FT4, could be undiagnosed as well, because those ranges have not adjusted.
Bruce, you can't just target numbers, out of the clear blue sky, because they sound good or because someone else had numbers like that...... you'll know you're where you need to be, when your symptoms are gone. Just because one person feels good with an FT3 at 3.5, doesn't mean that's the number you should target. I, personally, felt best at 3.7, but that may be too much or too little for someone else. Additionally, I didn't pick that number arbitrarily -- it came up on labs, when I felt best and when my level dropped, I didn't feel well.
I agree with Barb. She and I could be the poster children for the upper and lower ends of the ranges. My last FT3 was 2.5, and I feel great. You just have to find your own personal space.
I also agree about the hormones on demand. Since we no longer have that, I think once on meds, where we need to be changes quite a bit. We have to run hormones high enough to cover peak demand periods, and as a result, we probably have to be a little higher in the ranges than the "normal" population.
"tsh .45- 4.5 (i am aiming for 2.0) a friend of mine does not have thyroid disease, his is 1.54" You really can't aim for a number, but if you insist, please aim at something other than TSH. You've heard us talk about the limitations of TSH...really, it's totally irrelevant. You'd be much better off setting your sights on FT3...don't get me wrong, you still can't pick a number out of the air and shoot for it, but it's your FT3 level that will ultimately control how you feel more than any of the other tests.
Everyone is different. ...
Hard to tell...
Being a man with a woman's disease can be quite difficult at times. Y'all all answered the question, but no one answered my question. LOL
all i am asking is - in a normal every day human being, what is their t4 level. If you took 100 people and they all had healthy thyroids, and tested them, what would their t4 levels be?
this is more of a curiosity question that a co-roid and i were having as part of a discussion the other day.
Im just really interested in the ft4. I know barb and mrs. goolarra have higher tsh's but I'm just curious.