Thyroglobulin

Background

The thyroid gland is a small endocrine gland located in the base of the neck. It consists of two lateral lobes connected by an isthmus. The gland produces a variety of metabolic hormones in a negative biofeedback loop.

Thyroglobulin (Tg) is a large glycoprotein (MW 600,000) that is stored in the follicular colloid of the gland. Thyroglobulin functions as aprohormone in the intra-thyroid synthesis of T4 and T3. Lysosomes containing proteases cleave T4 and T3 from Tg, resulting in release of these hormones.

Thyroglobulin is present in the serum of normal healthy individuals and can be elevated in numerous disorders which disrupt thyroid tissue. Elevated circulating levels of Tg have been found in a number of thyroid Conditions including Hashimoto’s disease, Grave’s disease. Thyroid Adenoma, sub acute thyroiditis and thyroid carcinoma1.

Thyroid cancer is a relatively common form of cancer. It is not generally malignant, and normal life span can be obtained with appropriate follow-up and treatment. Females are affected 2 to 3 times more frequently than males. Thyroglobulin has become a useful tool in the follow-up of patients with differentiated carcinoma.

The thyroid is the only source of Tg, therefore, the serum Tg level will drop to a very low level or undetectable level after total or near-total thyroidectomy and successful radioiodine ablation of the residual thyroid tissue. A rise in serum level of Tg points to the recurrence of the disease. Thyroglobulin levels in patients who have undergone only partial thyroidectomy will retain measurable levels of Tg depending on how much tissue is remaining after surgery.

Reference ranges

Less than 55 ng/ml

Specimen requirements

Sample type:

• Serum

Sample identification:

• Three patient identifiers from
  • Name
  • D.O.B.
  • Address
  • N.H.S. number
  • Unit Number
  should match on the specimen and request form. This check may be performed prior to centrifugation by the Central Sort department.

Turnaround time

6 hours