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Thyroid Stimulating Hormone (TSH)
 

Panels › Hormone Panels › Thyroid Stimulating Hormone (TSH)

Thyroid Stimulating Hormone (TSH)

Significance
Thyroid-stimulating hormone is a glycoprotein hormone secreted by the anterior pituitary that stimulates the thyroid gland to synthesize and release thyroid hormones, Thyroxine (T4) and Triiodothyronine (T3). Secretion of TSH is under the control of a hypothalamic hormone, Thyrotropin releasing Hormone (TRH), which acts on the anterior pituitary to stimulate secretion of TSH. Measurement of TSH is helpful where clinical symptoms are consistent with either thyroid hormone deficiency (hypothyroidism) or excess (hyperthyroidism). Typical symptoms of hypothyroidism include weight gain, tiredness, dry skin, constipation, a feeling of being too cold, or frequent menstrual periods. Hyperthyroidism causes symptoms such as weight loss, rapid heart rate, nervousness, diarrhoea, a feeling of being too hot, or irregular menstrual periods. TSH levels can help determine whether hypothyroidism is due to a damaged thyroid gland or some other cause (i.e. pituitary gland or the hypothalamus). Other applications include monitoring thyroid gland function when under treatment for hyperthyroidism or monitor treatment with thyroid replacement medication, as well as diagnose and monitor female infertility problems. The incidence of thyroid related diseases increases after the age of 35. Expert recommendation is to screen women over 50, asymptomatic adults over 60, or those at high risk for thyroid disorders, such as pregnant and postpartum women. Among the secondary concerns are that Homocysteine and lipoprotein a levels may be increased in patients with primary hypothyroidism, potentially contributing to an increased risk of atherosclerotic disease. With overt hyperthyroidism the concerns are associated with increased bone turnover and reduction in bone mineral density, which is especially pronounced in estrogen deficient postmenopausal women.

Analysis
Determination of TSH is performed by enzyme immunoassay.

Patient Preparation
Morning specimen is preferred. Where possible/appropriate avoid medication (corticosteroids, levodopa, aspirin, heparin, dopamine, lithium, estrogens, androgens etc) that can alter TSH levels at least 48 hrs prior to specimen collection.

Specimen requirements
Serum specimen - from a plain redtop or a redtop gel (tiger top) tube. Separate serum from cells after centrifugation, if a plain redtop tube is used. Minimum volume required is 1 mL. Specimen should be kept refrigerated whenever possible.

Shipping Instructions
Ship specimen at ambient temperatures. For long distance shipping, ship with ice packs.

Additional information
http://www.labtestsonline.org/understanding/analytes/tsh/test.html