. Author manuscript; available in PMC: 2017 Dec 1.

Published in final edited form as: Eur J Endocrinol. 2016 Dec;175(6):R255–R263. doi: 10.1530/EJE-16-0193

Table 2.

Laboratory values by immunoassay and LC-MSMS on the same sample for a 68 year-old woman with persistent symptoms of hypothyroidism while on L-T4 therapy.

	Value	Reference range

Immunoassay results
FT4	1.2 ng/dL	0.8 – 1.5 ng/dL
FT3	2.5 pg/mL	1.8 – 4.2 pg/mL
TT3	99 ng/mL	90 – 215 ng/dL
T4	8.0 ug/dL	4.5 – 12.5 ug/dL

LC-MSMS results
FT4	1.2 ng/dL	0.8 – 2.0 ng/dL
FT3	1.5 pg/mL	1.5 – 6.0 pg/mL
TT3	64 ng/dL	80 – 187 ng/dL
TT4	7.2 ug/dL	4.9 – 10.5 ug/dL
rT3	8.7 ng/dL	9 – 21 ng/dL

T3 ng/dLx 0.0154 = T3 nmole/L

T4 ug/dL x 12.87=T4 nmole/L