1. TSH Thyroid Stimulating Hormone DIANA RUS

2. Thyroid stimulating hormone is released by the pituitary gland. It instructs the thyroid gland to release the thyroid hormones, T3 and T4. TSH is controlled by negative feedback by the thyroid hormones. Therefore, TSH measurement can be carried out to assess thyroid function. Figure 1: Thyroid functions. Source: https://www.aacc.org/publications/cln/ articles/2013/may/tsh-harmonization

3. Measurement of TSH is currently used as a first line thyroid function test. It can mainly be used to detect the following thyroid problems: Hypothyroidism (underactive thyroid): In this case TSH can be up to ten times higher than the normal serum concentration. Hyperthyroidism (overactive thyroid): TSH levels are low if the thyroid is underactive. High TSH levels can also indicate a TSH secreting tumour. If TSH levels are higher or lower than the normal range, further tests must be carried out to give a diagnosis. Diseases

4. Other Causes of abnormal TSH levels TSH measurement alone can not diagnose an individual with thyroid disease. There are other factors which affect thyroid levels: TSH levels can be elevated or lowered if the individual has a non thyroid illness or is recovering from an illness. This is in fact more common than hypo- or hyperthyroidism. Certain drugs can affect TSH secretion. Corticosteroids, for example, inhibit TSH secretion. If the patient is ambulatory and not on any drugs that affect TSH secretion it is a very reliable test for thyroid function.

5. Measurement in the Laboratory Immunometric assays are used to measure serum TSH levels. Third generation TSH assays are most commonly used in medical laboratories. This system is automated and they have a sensitivity of 0.01-0.02mlU/L. Excess monoclonal antibodies targeted to different TSH epitopes are added to the serum sample and incubated for up to two hours. Then a another antibody is added that targets different TSH epitopes and a non isotopic signal. This is incubated again and the unbound antibody is washed away. Chimeric monoclonal antibodies are used to stop heterophilic antibodies affecting results.

6. Home/Self Test Kits There are two types of home kits available: 1.Where the test is fully carried out at home. A kit is purchased online for as low as €14.90 and results can be read after ten minutes. Prima home test is an example of a company that produces these home tests. 2.Where the sample is taken at home and sent to a laboratory. In the US there is a kit available at a higher price of $30.95 and results are sent to a certified laboratory but results can take up to three weeks to be sent to the individual.

7. References Carole A. Spencer (2013). Assay of Thyroid Hormones and Related Substances. Thyroid Disease Manager. Available at: http://www.thyroidmanager.org/chapter/assay-of-thyroid-hormones-and-related- substances/#toc-4-serum-tsh-thyroid-stimulating-hormonethyrotropin-assays (Accessed 12 February 2016).http://www.thyroidmanager.org/chapter/assay-of-thyroid-hormones-and-related- substances/#toc-4-serum-tsh-thyroid-stimulating-hormonethyrotropin-assays James D. Faix, Linda M. Thienpont (2013). Thyroid-Stimulating Hormone: Why Efforts to Harmonize Testing Are Critical to Patient Care. Available at: https://www.aacc.org/publications/cln/articles/2013/may/tsh- harmonization (Accessed 13 February 2016).https://www.aacc.org/publications/cln/articles/2013/may/tsh- harmonization Salvatore D, Davies TF, Schlumberger MJ, et al. (2011). Thyroid physiology and diagnostic evaluation of patients with thyroid disorders. In: Melmed S, Polonsky KS, Larsen PR, et al., eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Elsevier Saunders. chap: 11. William J Marshall, Stephen K Bangert, Martha Lapsley (2012). Clinical Chemistry 7 th ed. Edinburgh, Mosby Elsevier. https://primahometest.com/thyroid-tsh-test http://www.homehealthtesting.com/thyroid-tsh-test-p-37.html