To convert from pmol/L to pmol/mg, you need to know the density of the specific substance you are working with, as it will determine how many milligrams are in a liter.

The general formula for conversion is:

pmol/mg = (pmol/L) / (mg/L)

To convert concentrations of T3 (triiodothyronine) and T4 (thyroxine) hormones from pmol/L to pmol/mg, you’ll need the molecular weights of these hormones and the density of the serum or plasma sample.

T3: approximately 651.97 g/mol

T4: approximately 776.87 g/mol

(make sure you got the right molecular weight!!!)

i.e. For T3: If you have a concentration of, say, 5 pmol/L:

• mg/L= [5 pmol/L × 651.97 g/mol] / 1000 = 3.26 mg/L
• pmol/mg = (5 pmol/L) / (3.26 mg/L) ≈1.53 pmol/mg

For T4, follow the same process using its molecular weight.

I hope this helps

Demos Kynigopoulos

Thank you for your answer.

You don't relate to the sample mass?

I believe it is not necessary as it is not a standard thing. The T3 and T4 levels are not the same in each animal. The same sample mass from 2 different animals may have different hormone concentrations