Laboratory Medicine Program

Thyroid stimulating hormone (TSH)
(TSH)

Clinical Decription:
Thyroid-stimulating hormone is as glycoprotein with two con-covalently subunits. The alpha subunit is similar to those of follicle-stimulating hormone (FSH), human chorionic gonadotropin (hCG), and luteinizing hormone (LH). The beta subunit of TSH is unique, which results in the specific biochemical and immunological properties of this hormone. TSH is synthesized with specific cell receptors on the thyroid cell surface and exerts two main actions. The first action is to stimulate cell reproduction and hypertrophy. Secondly, TSH stimulates the thyroid gland to synthesize and secrete T3 and T4. The ability to quantitate circulating levels of TSH is important in evaluating thyroid function. It is especially useful in; the deferential diagnosis primary (thyroid) from secondary (pituitary) and tertiary (hypothalamus) hypothyroidism. TSH levels are significantly elevated, while in secondary and tertiary hypothyroidism, TSH levels are low. TRH stimulation differentiates secondary and tertiary hypothyroidism by observing the change in patient TSH levels. Typically, the TSH response to TRH stimulation is absent in cases of secondary hypothyroidism and normal to exaggerated in tertiary hypothyroidism. Historically, TRH stimulation has been used to confirm primary hyperthyroidism indicated by elevated t3 and t4 levels and low or undetectable TSH levels TSH assays with increased sensitivity and specificity provide a primary diagnostic tool to differentiate hyperthyroid from euthyroid patients.

Method: Chemiluminometric technology

Component Tests Used: n/a

Reference Ranges Used:
0.35 - 4.94 mIU/L

Specimen Type: serum
Volume: 3 mL (minimum: 1 mL)

Shipping: room temperature or 4C

Special Instructions: Triple bolus - mark collection times on tubes. Centrifuge and aliquot.

Testing Schedule(s): Daily.

Turnaround Time: 1 day

For more information, call 416.340.5227 or 1.866.865.5227