Description
Thyroid Stimulating Hormone (TSH) is a key protein in the control of thyroid function. TSH is synthesised in the anterior pituitary which is stimulated by thyrotropin-releasing hormone (TRH) and inhibited by thyroid hormones in a classical endocrine negative feedback loop. TSH binding to its receptor on thyroid cells leads to the modulation of thyroidal gene expression. Physiological roles of TSH include the stimulation of differentiated thyroid functions, such as iodine uptake and organification, the production and release of iodothyronines from the gland and the promotion of thyroid growth. TSH also acts as a factor protecting thyroid cells from apoptosis and plays a critical role in ontogeny. see Also Thyroxine (T4), Free, Serum, and Thyroglobulin, Serum
Indications
Because free T4 and TSH are in a feedback relation, diseases of the thyroid or pituitary show predictable concordant relations between these indicators; either inverse, in the case of primary thyroid dysfunction, or direct, in the case of pituitary-dependent abnormalities. Subject to several assumptions, e.g., steady state and adequate assay sensitivity, this relation has high diagnostic sensitivity and specificity. However, in critical illness, a high proportion of alterations reflect discordant non-diagnostic changes when TSH and T4 are considered together. Moreover, TSH and T4 are helpful in the diagnosis of subclinical hypothyroidism where, T3 and T4 levels appear normal but with increased TSH. TSH levels may vary based on many variables including the time of the day the sample was aquired, pregnancy, illnesses and medications.In order to get the most accurate results, it's important to be consistent.
Sample Type, Quantity & Conditions
1 ml Serum 1 ml Li, Na, NH4+-Heparin, K3-EDTA, Sodium Citrate, or Sodium Fluoride/Potassium Oxalate Plasma Stability: 7 Days at 2-8 °C 1 Month at -20 °C
Special Precautions
Freeze only once.
Normal Range
Newborn: 0.70-15.20 μIU/mL 6 Days - 3 Months: 0.72-11.00 μIU/mL 4 Months - 12 Months: 0.73-8.35 μIU/mL 1 Year - 6 Years: 0.70-5.97 μIU/mL 7 Years - 11 Years: 0.60-4.84 μIU/mL 11 - 20 Years: 0.51-4.30 μIU/mL >20 0.30 - 4.20 μIU/mL
