Thyroid Tests by Nurse Practitioners
Choosing Wisely Canada Recommendation
- Don’t order thyroid function tests in asymptomatic patients.
- Don’t use Free T4 or T3 to screen for hypothyroidism or to monitor and adjust levothyroxine (T4) dose in patients with known primary hypothyroidism, unless the patient has suspected or known pituitary or hypothalamic disease.
- In most people, a normal Thyroid Stimulating Hormone (TSH) indicates either a normal endogenous thyroid function or an adequate T4 replacement dose.
- TSH only becomes unreliable in patients with known or suspected pituitary or hypothalamic disease when TSH cannot respond physiologically to altered T4 or T3.
- In stable patients, TSH needs to be monitored no more often than every six months.
- Costs per test are: TSH: $10, T4: $12, and T3: $9.
- 84% of TSH tests are ordered by FPs, as well as 79% of T4 tests, and 57% of T3 tests.
- The practice of endocrinologists is substantially different from that of primary care clinicians which accounts for the higher rate of T4 and T3 testing undertaken by endocrinologists.
T4 and T3 ordering is frequently coupled with TSH testing. This is usually unnecessary as reflex testing for T4 within laboratories is undertaken in patients with an abnormal TSH.
From 1 Apr 2014 – 31 Mar 2019 (5 years), there was a total of 795, 961 TSH tests ordered.
- From 1 Apr 2014 – 31 Mar 2019, there were a total of 795,961 TSH tests, 182,960 T4 tests and 23,693 T3 tests performed by clinicians.
- From 1 Apr 2014 – 31 Mar 2019, there were 18, 724 TSH tests ordered by NPs, 15% of which were accompanied by a T4 and/or T3 test order.
- 80% of tests were ordered by 22% of NPs (red line).
What You Can Do
- Routine screening for thyroid dysfunction is not recommended unless there are symptoms and signs of thyroid disease.
- TSH is the best initial test and an abnormal result will trigger laboratory reflex testing of additional thyroid function tests as indicated, in most laboratories.
- Thyroid dysfunction (hypo- or hyperthyroid) can be classified as overt or subclinical and treatment is guided by TSH results and the clinical situation.