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Test Name:
Insulin, Total, Timed, 90 Minutes
- SBMF No:
30047 - Performance Lab Name:
Automated Lab - Test Mnemonic:
INSULIN 90 - ABN:
Not required - CPT Code:
83525-91 - LOINC Code:
27330-0 - Also See:
30061 Insulin, Total, Timed, Baseline
30044 Insulin, Total, Timed, 30 Minutes
30046 Insulin, Total, Timed, 60 Minutes
30048 Insulin, Total, Timed, 120 Minutes - Spec Type:
Serum - Spec Container:
Gold top (SST) or red top (serum) tube - Alt Spec Type:
Plasma - Alt Spec Container:
Lavender top (EDTA) tube or green top (lithium heparin) tube - Pref Vol:
1.0 mL - Min Vol:
0.5 mL - Fasting:
Yes - Patient Prep:
Fasting at least 12 hours - Spec Collect:
Routine venipuncture
Collect at specified time interval – 90 minutes post-glucose dose - Spec Process:
Serum sample tubes, clot 30 minutes
Promptly centrifuge 15 minutes
Immediately transfer serum or plasma to separate plastic tube and freeze - Spec Store Transport:
Refrigerated (24 hours) or frozen (preferred) - Spec Stability:
After separation from cells:
4 hours room temperature (20-30°C)
24 hours refrigerated (2-8°C)
6 months frozen (-20°C) – Do not use frost-free units that undergo repeated freeze/thaw cycles. - Spec Reject:
Serum or plasma in contact with RBC more than 1 hour
Sample not frozen within 24 hours of collection
Hemolyzed sample - Methodology:
Electrochemiluminescent Immunoassay (ECLIA) - Use:
Utilized in the diagnosis and therapy of various disorders of carbohydrate metabolism, including diabetes mellitus and hypoglycemia - Clinical Significance:
Insulin is a peptide hormone with a molecular weight of approximately 6000 D. It is secreted by the B-cells of the pancreas and passes into circulation via the portal vein and the liver. Insulin is generally released in pulses, with the parallel glucose cycle normally about 2 minutes ahead of the insulin cycle.
The insulin molecule consists of two polypeptides, the a-chain with 21 and the ß-chain with 30 amino acids. Biosynthesis of the hormone takes place in the beta cells of the islets of Langerhans in the form of single-chain preproinsulin, which is immediately cleaved to give proinsulin. Specific proteases cleave proinsulin to insulin and C-peptide, which pass into the blood stream simultaneously. About half of the insulin, but virtually none of the C-peptide, is retained in the liver. Circulating insulin has a half-life of 3-5 minutes and is preferentially degraded in the liver, whereas inactivation or excretion of proinsulin and C-peptide mainly takes place in the kidneys. The amino acid sequence of insulin has remained surprisingly constant during evolution, with the result that prior to the development of genetically engineered human insulin it was possible to successfully use porcine or bovine insulin in the therapy of diabetes mellitus.
The action of insulin is mediated by specific receptors and primarily consists of facilitation of the uptake of sugar by the cells of the liver, fatty tissue and musculature; this is the basis of its hypoglycemic action.
Serum insulin determinations are mainly performed on patients with symptoms of hypoglycemia. They are used to ascertain the glucose-insulin quotients and for clarification of questions concerning insulin secretion, e.g., in the tolbutamide test and glucagons test or in the evaluation of oral glucose tolerance tests or hunger provocation tests.
Although the adequacy of pancreatic insulin synthesis is frequently assessed via the determination of C-peptide, it is still generally necessary to determine insulin. For example, therapeutic administration of insulins of non-human origin could lead to the formation of anti-insulin antibodies. In this case, measurement of the concentration of serum insulin shows the quantity of free, and hence biologically active, hormone, whereas the determination of C-peptide provides a measure of the patient’s total endogenous insulin secretion.
A disorder in insulin metabolism leads to massive influencing of a number of metabolic processes. Too low a concentration of free, biologically active insulin can lead to the development of diabetes mellitus. Possible causes of this include destruction of the beta cells (type I diabetes), reduced activity of the insulin or reduced pancreatic synthesis (type II), circulating antibodies to insulin, delayed release of insulin or the absence (or inadequacy) of insulin receptors. On the other hand, autonomous, non-regulated insulin secretion is generally the cause of hypoglycemia. This condition is brought about by inhibition of gluconeogenesis, e.g., as a result of severe hepatic or renal failure, islet cell adenoma, or carcinoma. Hypoglycemia can, however, also be facilitated intentionally or unintentionally (factitious hypoglycemia).
In three percent of persons with reduced glucose tolerance, the metabolic state deteriorates towards diabetes mellitus over a period of time. Reduced glucose tolerance during pregnancy always requires treatment. The clearly elevated risk of mortality of the fetus necessitates intensive monitoring.
- Reference Range:
90 minutes after 75 g glucose dose: 26.0-84.0 µU/mL - Additional Test Info:
Limitations and Interferences:
• In patients receiving therapy with high biotin doses (i.e., greater than 5 mg/day), no sample should be taken until at least 8 hours after the last biotin administration.
• Samples from patients treated with bovine or porcine insulin sometimes contain anti-insulin antibodies that can affect the test results.
• As with all tests containing monoclonal mouse antibodies, erroneous findings may be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies or have received them for diagnostic purposes.
• For diagnostic purposes, the results should always be assessed in conjunction with the patient’s medical history, clinical examination and other findings. - Day Run:
Sun-Sat (daily) - Time Run:
2:00 pm - Time Reported:
8 hours - Test Type:
HORMONE
