Test Name: TSH, Blood
Specimen Type: Serum
Specimen Required: 3-5 Cc Yellow Top Gel Vial
Day Performed: Daily
Reporting Time: 8-24 Hours
Methodology: Beckman Coulter Access II/ Snibe Maglumi 4000
CLINICAL SIGNIFICANCE:
A higher-than-normal TSH level is most often due to an underactive thyroid gland (hypothyroidism). There are many causes of this problem.
A lower-than-normal level may be due to an overactive thyroid gland, which can be caused by:
- Graves disease
- Toxic nodular goiter or multinodular goiter
- Too much iodine in the body (due to receiving iodine contrast used during imaging tests, such as CT scan)
- Taking too much thyroid hormone medicine or prescribed natural or over-the-counter supplements that contain thyroid hormone
Use of certain medicines may also cause a lower-than-normal TSH level. These include glucocorticoids/steroids, dopamine, certain chemotherapy drugs, and opioid painkillers such as morphine.
References:
- Guber HA, Oprea M, Rusell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022: chap 25.
- Jonklaas J, Cooper DS. Thyroid. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020: chap 213.
- Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020: chap 11.
- Weiss RE, Refetoff S. Thyroid function testing. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016: chap 78.