Thyroglobulin

Pick Ordered or Not ordered to see the note.

Indicated when

• —Surveillance for recurrent or persistent disease in a patient previously treated for differentiated thyroid cancer, typically after thyroidectomy with or without radioiodine ablation [1]

Not indicated when

• —Screening for thyroid cancer in a patient with no personal history of differentiated thyroid cancer, including a patient worried about a thyroid nodule that hasn't been biopsied [1]
• —Investigating fatigue, general thyroid symptoms, or as part of a routine or 'wellness' thyroid panel

Why not

Thyroglobulin is a protein made by normal and by well-differentiated cancerous thyroid tissue alike, so it is not a screening test: an elevated level in someone who has never had thyroid cancer, or whose thyroid gland is still in place, does not point to cancer specifically and cannot be interpreted the way it can be after a thyroidectomy, when the gland that normally makes it is gone. Ordered outside its follow-up role, it mainly generates a hard-to-interpret result and, if thyroid peroxidase or thyroglobulin autoantibodies are also present, can be falsely low or unreliable regardless of the clinical situation [1].

Better first step

For a worried-well patient with no history of thyroid cancer, evaluate any palpable thyroid nodule or enlargement with TSH and thyroid ultrasound, and use fine-needle aspiration biopsy criteria to decide whether cancer needs to be ruled out, rather than ordering thyroglobulin [1, 2].

Typical ND rationale

An ND may include thyroglobulin as part of a broader hormone or tumour-marker panel, reasoning that it is a thyroid-related marker and checking it, along with other markers, offers reassurance or early warning about thyroid cancer.

Ontario coverage & CONO orderability

OHIP status

insured

Thyroglobulin is listed by name (L609) in the 2026 Schedule with a standard professional fee ($11.78), so it is insured when a physician who has clinically assessed the patient orders it. The Schedule text does not itself state a clinical restriction (unlike, for example, PSA or vitamin D), but its validated clinical use is narrow; see indicated_when. ND-ordered testing is patient-paid regardless (Reg. 552 s.22).

CONO orderable

Yes — CONO list #117

CONO list item 117, blood: 'Thyroglobulin.'

Linked conditions

• Tumour markers to check for 'hidden' cancer ↗

Counselling script

“Thyroglobulin isn't a screening test for thyroid cancer, it's a follow-up test used after someone has already been treated for a specific type of thyroid cancer. Since that doesn't apply to you, a thyroglobulin level wouldn't tell us anything useful and could actually be confusing. If you're worried about a lump or your thyroid in general, let's start with an exam and, if needed, an ultrasound instead.”

Revisit if

• —Palpable thyroid nodule or new thyroid enlargement found on exam
• —Prior diagnosis of differentiated thyroid cancer comes to light
• —New symptoms suggestive of thyroid dysfunction develop

References

1. [1]American Thyroid Association (2015). 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer. linkolder guidelineSerum thyroglobulin is used for long-term surveillance for recurrent disease in patients previously treated for differentiated thyroid cancer, not for screening
2. [2]Canadian Society of Endocrinology and Metabolism / Choosing Wisely Canada (2026). Endocrinology and Metabolism: Seven Tests and Treatments to Question. linkThyroid imaging and work-up should follow palpable abnormality or abnormal thyroid function, not be used as an undirected screen