What is the role of lab tests in the workup of insulin resistance?

Updated: Aug 07, 2019
  • Author: Samuel T Olatunbosun, MD, FACP, FACE; Chief Editor: George T Griffing, MD  more...
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Answer

Routine laboratory measurements in the evaluation of patients with insulin resistance syndrome include the following:

  • Plasma glucose level (fasting, random, and oral glucose tolerance test) - Diagnosis and monitoring of glucose intolerance (diabetes mellitus, impaired glucose tolerance [IGT], impaired fasting glucose [IFG]).

  • Insulin resistance - May also be associated with hypoglycemia (autoimmune conditions).

  • Glycohemoglobin level – Used to assess chronic hyperglycemia.

  • Fasting insulin level - A measure of the degree of insulin resistance in many patients with insulin resistance syndrome.

  • Lipid profile (fasting total cholesterol, low-density lipoprotein [LDL], high-density lipoprotein [HDL], cholesterol, triglyceride) - Insulin resistance syndrome characterized by elevated LDL-B levels (small, dense, pattern B), high triglyceride levels, and reduced HDL-C levels.

  • Combined use of insulin and lipid markers in atherosclerosis - Fasting insulin, apolipoprotein B, and small LDL levels are more biologically significant than are standard lipid tests. Elevations in the 3 markers increase the risk of coronary artery disease by nearly 20-fold.

  • Electrolyte levels (BUN [blood urea nitrogen], creatinine, and uric acid levels) - Hyperuricemia is common and is often considered a component of the metabolic syndrome.

  • Urinalysis - Microalbuminuria is a marker of endothelial dysfunction.

  • Homocysteine (H[e]) - An elevated level is a risk factor for atherosclerosis, which predicts macrovascular disease. levels are regulated by insulin.

  • Plasminogen activator inhibitor (PAI)-1 - An elevated level is associated with insulin resistance syndrome and is correlated with obesity, waist-to-hip ratio, hypertension, fasting and postprandial insulin levels, proinsulin levels, fasting glucose levels, and elevated triglyceride and LDL levels. [50] An increased PAI-1 level signifies impaired fibrinolysis, thus indicating increased risk of atherosclerosis.

Other laboratory studies include measurement of fibrinogen levels and testing of endothelial function. An increased fibrinogen level is a feature of insulin resistance syndrome. Endothelium plays an important role in insulin action, including in the regulation of tissue blood flow and in insulin delivery to interstitium. Endothelial dysfunction is an important component of insulin resistance syndrome and includes reduced capillary formation, reduced surface area, and abnormal reactivity of endothelium. [51]

Most recently, serum WISP-1/CCN4 level (WNT1 inducible signaling pathway protein 1), a novel pro-inflammatory adipokine, was proposed as a suitable biomarker of obesity, and the levels correlate with anthropometric indices of obesity. [52]

Biochemical changes associated with endothelial dysfunction include (1) reduced nitric oxide and prostacyclin levels, (2) increased endothelin and angiotensin activity, and (3) increased local and systemic inflammation (increased C-reactive protein [CRP] levels). [3] Blood testing for CRP measurement is widely available. Smoking and abnormal lipids are major contributors to endothelial dysfunction.


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