RT Book, Section
A1 Fitzgerald, Paul A.
A2 Papadakis, Maxine A.
A2 McPhee, Stephen J.
A2 Rabow, Michael W.
SR Print(0)
ID 1166173214
T1 Thyroid Testing
T2 Current Medical Diagnosis and Treatment 2020
YR 2020
FD 2020
PB McGraw-Hill Education
PP New York, NY
SN 9781260455281
LK accessmedicine.mhmedical.com/content.aspx?aid=1166173214
RD 2022/05/27
AB Assays  for  FT4,  total  triiodothyronine  (T3),  and  free  triiodothyronine  (FT3)  have  largely  supplanted  measurements  of  total  T4,  resin  T3  uptake  (RT3U),  and  free  thyroxine  index  (FT4I).  It  is  particularly  important  to  determine  "free"  serum  levels  (FT4  and  FT3)  in  conditions  associated  with  high  circulating  levels  of  thyroxine-binding  globulin  (TBG),  such  as  during  therapy  with  oral  estrogen.  Ultrasensitive  assays  for  serum  TSH  have  largely  replaced  older  TSH  assays.  Table  26–2  shows  the  appropriate  use  of  thyroid  tests.