Synonym
Thyrotropin
Adult patient:
Clotted blood tube
(Serum gel separator clot activator tube)
Minimum blood volume: 5 mL
Paediatric patient:
Paediatric clotted blood tube
Number of vials: 2
Minimum blood volume: 1.6 mL
Authorisation code required
No
24 Hr available service
No
Method
Immunoassay
Reference interval
(I) Non-pregnant individual:
| Age | Range |
| 0 - < 6 d | 0.70 - 15.20 mIU/L |
| > 6 d - < 90 d | 0.72 - 11.00 mIU/L |
| > 90 d - < 1 y | 0.73 - 8.35 mIU/L |
| > 1 y - < 6 y | 0.70 - 5.97 mIU/L |
| > 6 y - < 11 y | 0.60 - 4.84 mIU/L |
| > 11 y - 998 y | 0.27 - 4.20 mIU/L |
(Source: Reference Intervals for Children and Adults 2009: Elecsys Thyroid Tests)
(II) During pregnancy (gestational age-specific):
Gestation (week) |
sTSH (mIU/L) |
FT3 (pmol/L) |
FT4 (pmol/L) |
< 5 |
0.38 - 4.84 |
3.49 - 5.70 |
11.6 - 23.0 |
> 5 - 6 |
0.22 - 4.11 |
3.54 - 5.79 |
11.9 - 23.8 |
> 6 - 7 |
0.09 - 3.35 |
3.58 - 5.90 |
12.1 - 24.5 |
> 7 - 8 |
0.05 - 3.02 |
3.59 - 5.92 |
12.1 - 24.5 |
> 8 - 9 |
0.03 - 2.88 |
3.59 - 5.92 |
12.1 - 24.5 |
> 9 - 10 |
0.03 - 2.88 |
3.57 - 5.87 |
11.9 - 23.9 |
> 10 - 11 |
0.04 - 2.93 |
3.54 - 5.81 |
11.7 - 23.3 |
> 11 - 12 |
0.05 - 3.03 |
3.51 - 5.74 |
11.4 - 22.8 |
> 12 - 13 |
0.06 - 3.14 |
3.47 - 5.66 |
11.2 - 22.2 |
> 13 - 14 |
0.08 - 3.27 |
3.43 - 5.57 |
11.0 - 21.6 |
> 14 - 15 |
0.09 - 3.40 |
3.39 - 5.49 |
10.7 – 21.0 |
> 15 - 16 |
0.11 - 3.52 |
3.35 - 5.40 |
10.5 - 20.5 |
> 16 - 20 |
0.15 - 3.78 |
3.25 - 5.20 |
10.1 - 19.4 |
> 20 - 32 |
0.23 - 4.18 |
3.03 - 4.75 |
9.2 - 17.4 |
> 32 - 36 |
0.31 - 4.54 |
2.94 - 4.56 |
9.0 - 17.0 |
> 36 |
0.44 - 5.07 |
2.97 - 4.62 |
9.2 - 17.4 |
(Source: Thyroid. 2020 Apr;30(4): 598 - 608)
Clinical indication
TSH estimation by a high sensitivity assay is now accepted as the first line test for assessment of thyroid function.
Monitoring of patients on thyroid replacement or suppressive therapy
Result interpretation
TSH has been adopted as the initial test of thyroid function as it is more sensitive than free T4 to alterations of thyroid status in patients with primary thyroid disease.
High levels are found in primary hypothyroidism.
Successful thyroid replacement therapy should be associated with a return of TSH to within the reference interval, however this may take several weeks to achieve.
Suppressed levels are found in hyperthyroidism; very rarely, hyperthyroidism may be due to pituitary overproduction of TSH.
In the treatment of thyroid cancer, TSH should be suppressed, but not to undetectable levels.
In hypopituitarism, levels are usually low but may be within the reference interval.
Measurement of uncertainty
Frequency of measurement
Daily