Blast!........I hoped that you wouldn't have picked that up.........;-)
There is an has been a controversy raging over the past four decades concerning the importance of T3.
The medical profession says that it is insignificant and the Thyroid Forums say, the medical profession is wrong.
Levothyroxine contains T4 but NOT T3......but natural desiccated thyroid does contain T3 and T4 but is more expensive.
What do i think? I think that the importance of T3 is exaggerated and the lack of T3 does not contribute to one's symptoms........my opinion only.
I have simplified this for you so as you can understand the problem.
I would suggest that you advice your sister to see her GP.......who will know *** all about the problem.
If Peter Pedant and or slaney see this thread then perhaps their input would hold more weight than mine.
Personally, i would be happy with those thyroid results of your sister's.