Thyroid Hormones (FT4, FT3): What's Optimal?

[Mike Lustgarten]

 

[Alex K Chen]

 

Quote

 

To convert 1.85 uIU/mL to pmol/L for FT4, we use the conversion factor of 1 uIU/mL = 12.87 pmol/L.

1.85 uIU/mL × 12.87 = 23.81 pmol/L

So, an FT4 level of 1.85 uIU/mL is equivalent to 23.81 pmol/L.

Now, let's determine the percentile for an FT4 level of 23.81 pmol/L. Percentiles indicate the percentage of a population that has a value lower than the given value. However, to calculate the exact percentile, we would need to know the distribution of FT4 levels in the specific population being considered.

Given the general reference range for FT4 in adults, which is 9.0-23.0 pmol/L, we can make an approximate estimation:

• An FT4 level of 23.81 pmol/L is slightly above the upper limit of the typical reference range.
• This suggests that the FT4 level is relatively high compared to the general population.
• Without knowing the exact distribution, we can estimate that the percentile for 23.81 pmol/L is likely to be above the 90th percentile, indicating that less than 10% of the population has an FT4 level higher than 23.81 pmol/L.
• ==

my total T3 is 48 ng/dL which is low...

 

the green range for that diagnostic is 0.27 to 4.2..

Edited May 26 by Alex K Chen

[Alex K Chen]

 

Quote

 

To convert 1.85 uIU/mL to pmol/L for FT4, we use the conversion factor of 1 uIU/mL = 12.87 pmol/L.

1.85 uIU/mL × 12.87 = 23.81 pmol/L

So, an FT4 level of 1.85 uIU/mL is equivalent to 23.81 pmol/L.

Now, let's determine the percentile for an FT4 level of 23.81 pmol/L. Percentiles indicate the percentage of a population that has a value lower than the given value. However, to calculate the exact percentile, we would need to know the distribution of FT4 levels in the specific population being considered.

Given the general reference range for FT4 in adults, which is 9.0-23.0 pmol/L, we can make an approximate estimation:

• An FT4 level of 23.81 pmol/L is slightly above the upper limit of the typical reference range.
• This suggests that the FT4 level is relatively high compared to the general population.
• Without knowing the exact distribution, we can estimate that the percentile for 23.81 pmol/L is likely to be above the 90th percentile, indicating that less than 10% of the population has an FT4 level higher than 23.81 pmol/L.

 

the green range for that diagnostic is 0.27 to 4.2..

For T3...

my total T3 is 48 ng/dL which is tagged as low...

I apologize for the confusion in my previous response. You asked about converting 48 ng/dL of total T3 (triiodothyronine) to pmol/L, not free T3 (FT3). Let me provide the correct conversion for total T3.

To convert 48 ng/dL of total T3 to pmol/L, we need to use the appropriate conversion factor for total T3.

For total T3, the conversion factor is:
1 ng/dL = 0.0154 nmol/L

First, let's convert 48 ng/dL to nmol/L:
48 ng/dL * 0.0154 = 0.7392 nmol/L

Now, to convert nmol/L to pmol/L, we multiply by 1000 (since 1 nmol = 1000 pmol):
0.7392 nmol/L * 1000 = 739.2 pmol/L

Therefore, 48 ng/dL of total T3 is equivalent to 739.2 pmol/L.

The typical reference range for total T3 in adults is approximately:
1.2-3.1 nmol/L or 1200-3100 pmol/L

Comparing the converted value of 739.2 pmol/L to this reference range, we can see that it falls within the normal range for total T3.

To estimate the percentile, we would need more specific information about the distribution of total T3 levels in the population. However, given that 739.2 pmol/L is within the normal range, it is likely to be around the 50th percentile, meaning that approximately half of the population would have a total T3 level lower than this value, and half would have a higher value.

It's important to note that the interpretation of total T3 levels should be done in the context of the individual's clinical presentation, other thyroid function tests, and the specific reference range provided by the laboratory.

In summary, 48 ng/dL of total T3 converts to 739.2 pmol/L. This value falls within the typical reference range for adults and is likely to be around the 50th percentile, indicating a normal total T3 level.

 

 

====

To convert 48 ng/dL of FT3 (free triiodothyronine) to pmol/L, we need to use the appropriate conversion factor. The conversion factor for FT3 is different from the one used for FT4.

For FT3, the conversion factor is:
1 ng/dL = 1.536 pmol/L

To convert 48 ng/dL to pmol/L, we multiply 48 by 1.536:

48 ng/dL * 1.536 = 73.728 pmol/L

Therefore, 48 ng/dL of FT3 is equivalent to 73.728 pmol/L.

Now, let's compare this value to the typical reference range for FT3 in adults, which is approximately 3.5-6.5 pmol/L.

An FT3 level of 73.728 pmol/L is significantly above the upper limit of the reference range. This indicates that the FT3 level is highly elevated compared to the general population.

Given the substantial elevation above the reference range, it is likely that an FT3 level of 73.728 pmol/L would be above the 99th percentile. This means that less than 1% of the population would have an FT3 level higher than 73.728 pmol/L.

However, it's crucial to note that such a highly elevated FT3 level is of significant clinical concern and would require further investigation and medical attention. An FT3 level this high could be indicative of a serious thyroid disorder or other underlying health conditions.

In summary, 48 ng/dL of FT3 converts to 73.728 pmol/L. This value is substantially above the typical reference range for adults and would be considered highly elevated, likely above the 99th percentile. Such a high FT3 level warrants prompt medical evaluation and management.

 

 

[Mike Lustgarten]

TSH is generally reported in uIU/mL-what's your FT4?

[Alex K Chen]

1.85 uIU/mL it was reported as

[Mike Lustgarten]

Hmm, I've yet to see a lab report FT4 in uIU/ml. Usually pmol/L or ng/dL