Changes to Thyroid Hormone Testing – Provincial Harmonization
As of June 21, 2022, three key changes were made to thyroid testing across the province:

1. Updated pediatric and adult reference intervals for TSH, free T4 (fT4) and free T3 (fT3) (Table 1).

2. Updated progressive TSH algorithm (Figure 1).

3. Implementation of a standardized comment to automatically append to females of child-bearing age that includes a link for gestational age-specific reference intervals.
The above changes were made to promote provincial harmonization using a very large Alberta dataset. TSH, fT4 and fT3 results were analyzed provincially across multiple sites and with different assays. This confirmed assay comparability so that reference intervals and cutoffs could be aligned. Endocrinologists across the province were consulted in the process. In addition, the updated and optimized progressive TSH algorithm will now only reflex to fT4 when TSH is suppressed. This will improve laboratory follow-up testing, test utilization, and costs when screening and monitoring primary thyroid disease in the community, without compromising patient care. The availability of gestational age-specific reference intervals for thyroid tests across the province will assist in appropriate assessment and management of thyroid dysfunction in pregnancy.
For more information and laboratory contacts, review the Laboratory Bulletin:
Table 1. Updated Thyroid Hormone Reference Intervals
Reference Interval


0 – <30 days

1.23 – 25.00

30 days – <1 year

1.00 – 6.80

≥1 year

0.20 – 6.50

FT4 (pmol/L)

0 – <15 days

13.5 – 50.0

15 days – <30 days

8.7 – 32.5

≥ 30 days

10.0 – 25.0

FT3 (pmol/L)

0 – <30 days

4.2 – 13.0

30 days – <1 year

5.1 – 8.6

1 – <14 years

4.4 – 8.1

14 – <18 years 

3.5 – 7.4

≥ 18 years

3.0 – 6.5

Figure 1. Updated Progressive TSH Algorithm

© 2022 Alberta Medical Association; All rights reserved

The opinions expressed in AMA publications are those of the authors and do not necessarily reflect the opinions or positions of the Alberta Medical Association, its Board of Directors or members.

The Alberta Medical Association does not assume responsibility or liability for damages arising from any error or omission or from the use of any information or advice contained in these materials. Advertisements included in our publications are not necessarily endorsed by the Alberta Medical Association.

The Association reserves the right to edit any submissions that are accepted to appear in any of our publications or platforms. Please consult our editorial guidelines for tips on submissions or advertising.

Our mailing address is:
12230 106 Ave NW
Edmonton, AB T5N 3Z1