The RCPA provides guidance on thyroid function testing

Today, the Royal College of Pathologists of Australasia (RCPA) provides a new position statement to offer guidance on thyroid function testing in the Australian and New Zealand context in the adult population.  The position statement provides a summary of the epidemiology of thyroid disease and the technical aspects of testing, and outlines recommendations for thyroid function testing for diagnosis and monitoring of thyroid disease.

Dr Michael Harrison, President of the RCPA, said,

“The College guidelines do not support general population or opportunistic screening for thyroid disease however, active case finding is recommended in patients at high risk of developing thyroid disease, or where there is a clinical suspicion based on relevant history, symptoms, test results or signs at presentations.  This might include: hypercholesterolemia; mild anaemia; hyponatremia; increased serum CK; muscle weakness; with changes, osteoporosis; and recent onset arrhythmia.”

“Evidence shows that screening for thyroid disease in asymptomatic adults does not improve quality of life or produce clinically meaningful improvement in BMI (body mass index), BP (blood pressure), bone mineral density or lipid levels.  Certain subgroups of the population however, are at higher risk of developing thyroid disease and in these groups, active case identification is beneficial.”

High risk subgroups include individuals in areas of iodine deficiency, personal or family history of thyroid disease, ingestion of iodine containing substances including amiodarone, lithium treatment, previous neck irradiation, type 1 diabetes mellitus and other autoimmune diseases, Down syndrome, Turners syndrome and advancing age.

Thyroid Stimulating Hormone (TSH) is generally the initial investigation for thyroid disease, however Dr Harrison explains that in some cases, free hormone assessment may be required in addition to TSH.

“In certain situations, patients may require free hormone assessment in addition to TSH for diagnosis, in particular in the context of known or suspected pituitary disease.  If TSH is abnormal, either above or below limits of the laboratory reference intervals, free tetraiodothyronine (free T4) should be requested and in some cases, further investigation with free triiodothyronine (free T3) is indicated.  Free T4 and/or free T3 should never be requested in isolation.

The RCPA also outlines the following guidelines for patients receiving thyroid treatment:

• Patients undergoing therapy with anti-thyroid drugs should have monitoring with TSH, free T4 and free T3 in the initial period of anti-thyroid medication dose adjustment.
• Patients receiving thyroxine replacement therapy for hypothyroidism should have monitoring of TSH, usually 6-8 weeks following dose adjustment, with the aim of normalising the TSH.
• Free T3 measurement is indicated in assessment of hyperthyroidism, treatment of hyperthyroidism and in monitoring of patients on T3 therapy, but is not indicated in monitoring of patients receiving levothyroxine therapy.
• There are no situations where measurement of reverse T3 is validated.

To view the RCPA’s full position statement on thyroid function testing for adult diagnosis and monitoring, please visit the College website - http://www.rcpa.edu.au/Thyroid-Function-Testing-for-Adult-Diagnosis