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abbreviation for thyrotropin-releasing factor. See thyrotropin-releasing hormone.


A gene on chromosome 5q31.1 that encodes interleukin-5, a cytokine which acts as a  growth and differentiation factor for B cells (inducing the terminal differentiation of late-developing B-cells to immunoglobulin secreting cell) and eosinophils, for the latter of which IL5 is a key regulator of eosinopoiesis, eosinophil maturation and activation.


Synonym/acronym: Siderophilin, TRF.

Common use

To assess circulating iron levels related to dietary intake to assist in diagnosing disorders such as iron deficiency anemia or hemochromatosis.


Serum (1 mL) collected in a gold-, red-, or red/gray-top tube.

Normal findings

(Method: Nephelometry)
AgeConventional UnitsSI Units (Conventional Units × 0.01)
Newborn130–275 mg/dL1.3–2.75 g/L
1–9 yr180–330 mg/dL1.8–3.3 g/L
10–19 yr195–385 mg/dL1.95–3.85 g/L
 Male215–365 mg/dL2.2–3.6 g/L
 Female250–380 mg/dL2.5–3.8 g/L


Transferrin is a glycoprotein formed in the liver. Its role is the transportation of iron, obtained from dietary intake or RBC breakdown; normally one-third of available transferrin is saturated. Inadequate transferrin levels can lead to impaired hemoglobin synthesis and anemia. Transferrin is subject to diurnal variation, and it is responsible for the variation in levels of serum iron throughout the day. (See monograph titled “Iron-Binding Capacity [Total], Transferrin, and Iron Saturation.”)

This procedure is contraindicated for



  • Determine the iron-binding capacity of the blood
  • Evaluate iron metabolism in iron-deficiency anemia
  • Evaluate nutritional status
  • Screen for hemochromatosis

Potential diagnosis

Increased in

  • Estrogen therapy (estrogen stimulates the liver to produce transferrin)
  • Iron-deficiency anemia (the liver produces transferrin in response to decreased iron levels)
  • Pregnancy (the liver produces transferrin in response to anemia of pregnancy)

Decreased in

    Acute or chronic infection (a negative acute-phase reactant protein whose levels decrease in response to inflammation) Cancer (especially of the gastrointestinal tract) (related to malnutrition) Excessive protein loss from renal disease (related to increased loss from damaged kidney) Hepatic damage (related to decreased synthesis in the liver) Hereditary atransferrinemia Malnutrition (related to a protein-deficient diet that does not provide the nutrients required for synthesis)

Critical findings


Interfering factors

  • Drugs that may increase transferrin levels include carbamazepine, danazol, mestranol, and oral contraceptives.
  • Drugs that may decrease transferrin levels include cortisone and dextran.
  • Transferrin levels are subject to diurnal variation and should be collected in the morning, when levels are highest.
  • Failure to follow dietary restrictions before the procedure may cause the procedure to be canceled or repeated.

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in evaluating for anemia.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s hematopoietic system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Instruct the patient to fast for at least 12 hr before specimen collection.
  • Note that there are no fluid or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Ensure that the patient has complied with dietary restrictions; ensure that food has been restricted for at least 12 hr prior to the procedure.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Instruct the patient to resume usual diet, as directed by the HCP.
  • Nutritional Considerations: Educate the patient with abnormal iron values that numerous factors affect the absorption of iron, enhancing or decreasing absorption regardless of the original content of the iron-containing dietary source. Patients must be educated to either increase or avoid intake of iron and iron-rich foods depending on their specific condition; for example, a patient with hemochromatosis or acute pernicious anemia should be educated to avoid foods rich in iron. Consumption of large amounts of alcohol damages the intestine and allows increased absorption of iron. A high intake of calcium and ascorbic acid also increases iron absorption. Iron absorption after a meal is also increased by factors in meat, fish, and poultry. Iron absorption is decreased by the absence (gastric resection) or diminished presence (use of antacids) of gastric acid. Phytic acids from cereals, tannins from tea and coffee, oxalic acid from vegetables, and minerals such as copper, zinc, and manganese interfere with iron absorption.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family. Educate the patient regarding access to nutritional counseling services. Provide contact information, if desired, for the Institute of Medicine of the National Academies (
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include A/G, cancer antigens, CBC, CBC RBC count, CBC RBC indices, CBC RBC morphology, ferritin, iron/TIBC, prealbumin, and total protein.
  • Refer to the Hematopoietic System table at the end of the book for related tests by body system.


thyrotropin releasing factor.
References in periodicals archive ?
048 for sample c) was well correlated with mean the TRF length by Southern blotting (8.
TRF was measured immunologically on either the Behring Nephelometer II (Behring Diagnostics) or the Beckman Array (r) 360-CE (Beckman Instruments), or both, with respective calibrators from Behring or Beckman.
The TRF is an instrument derived from the CBCL, administered to teachers, educational consultants, and other professionals involved in the child's educational development, so that they can also provide data on the most frequent behavior problems observed.
Figure 2 shows the results of pre-treatment of this assay with TRF and [alpha]-TCP, which indicated that MMP reached at 75.
Finally, we compared the estimated association between WMn and TRF internalizing behavior with that for the association between WMn and TRF externalizing behavior using the Wald statistic.
Further, consistent with the above results, the management teams of SEO firms have significantly larger TRF scores as compared to IPO firms.
As described earlier, LAF and TRF participants watched the same lesson and video clips during the intervention but answered different questions.
Using the telomere sequence information, TRF analyses demonstrated that telomeres of Symbiodinium isolated from M.
Non-parametric paired samples statistical analyses were used to analyze pre- and post-test TRF scores.
The focus of TRF is to provide clean and healthy environment at schools along with basic facilities to improve the quality of education by modern means of learning and to grant relief and assistance to the needy during natural calamities such as famine, earthquake, flood, fire, persistence, and to give donations and other assistance to institutions, establishment or persons engaged in such relief work.
The magnitude and range of acute health problems associated with TRF usage has not been described previously.