Lab data 2

• Liver


  • Largest solid organ in the human body
  • Plays a central role in all of the body's biochemistry
• Liver function tests


  • Can give a clearer picture of any of the functions of the liver: synthesis, excretion, or detoxification
  • Can help indicate liver injury
• Bilirubin


  • Reddish-yellow pigment produced during the normal breakdown of RBC
  • Excreted in bile, into the duodenum
  • Circulates in the bloodstream in two forms: indirect (unconjugated) and direct (conjugated)
• • Normal values for total bilirubin: 0.1 to 1.2 mg/dL
  • Normal values for direct bilirubin: less than 0.3 mg/dL
• Increase in total bilirubin and indirect bilirubin, but not direct bilirubin

  Indication of RBC hemolysis
• Elevated levels of direct bilirubin

  Associated with hepatocellular diseases
• Excessive total bilirubin


  Patients will exhibit signs of jaundice, which could result in kernicterus in infants and children
• Bilirubin excretion


  1. Conjugated bilirubin is excreted with the bile into the duodenum

  2. Conjugated bilirubin is converted by bacteria into urobilinogen

  3. Most urobilinogen is excreted in the feces, some is reabsorbed into the blood
• Complete bile duct obstruction


  No urobilinogen is formed, stools become gray-white or clay-colored, conjugated bilirubin is reabsorbed into the bloodstream and spilled into the urine
• False-positive results may occur in patients taking phenazopyridine or phenothiazines, as both the drugs and bile pigments in urine can cause an orange discoloration
• Alkaline phosphatase (ALP)


  • Enzyme produced mainly in the liver and bone, but can also be found in the kidneys, intestines, and placenta
  • Excreted by the liver into the bile, a sensitive indicator of biliary obstruction
• Normal values for ALP: 30-120 U/L (depending on age and assay)
• Increased concentrations of ALP

  May indicate hepatitis, liver cirrhosis, hepatic cancer, or gallstones
• High ALP levels


  May indicate an overreactive parathyroid gland, rickets, Paget's disease, or bone cancer
• Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT)


  • Enzymes located inside the hepatocytes, function to assist with various metabolic pathways
  • Any injury to these tissues will release the aminotransferases into the systemic circulation and result in their elevation
• Normal values for AST and ALT: 0-35 U/L (depending on age and assay)
• Increased concentrations of AST and ALT

  Associated with hepatitis, and alcoholic liver diseases
• Elevated levels of AST and ALT

  Could also be seen with drug toxicity or interference with drugs such as acetaminophen, erythromycin, or levodopa
• Thyroid gland


  • Produces three hormones: Triiodothyronine (T3), Tetraiodothyronine (T4), and Calcitonin
  • The two main hormones are T3 and T4, produced in the follicular epithelial cells of the thyroid, with iodine being one of the major components of both hormones
• Thyroid-Stimulating Hormone (TSH) test


  Measures the level of circulating TSH, used to screen for and diagnose thyroid disorders, and for routine monitoring during hypothyroidism treatment
• Normal values for TSH: 0.5 to 5 microunits per milliliter (µU/mL)
• Elevated TSH level


  Most often due to hypothyroidism
• Reduced TSH level


  Most often due to hyperthyroidism
• Triiodothyronine (T3)


  The more potent form of circulating thyroid hormone, usually used in the diagnosis of hyperthyroidism
• Normal values for T3: 1.2-3.1 mIU/L
• High levels of T3

  Usually seen in patients with hyperthyroidism, as well as in those with Graves' disease
• Decreased T3 levels


  Associated with hypothyroidism and/or malnutrition
• Drugs like corticosteroids and propranolol

  Decrease the conversion of T4 to T3, may result in reduced levels of T3
• Amiodarone


  Due to its high iodine content, may induce hypothyroidism or thyrotoxicosis, and should be avoided in patients on medications to manage thyroid abnormalities
• Lipid profile


  • Commonly used as part of a cardiac risk assessment, to determine an individual's likelihood of heart disease, and to assist in decision-making on what treatment may be best
  • Primarily comprises the measurement of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TGs)
• Low-Density Lipoprotein Cholesterol (LDL-C)


  • Approximately 60%-70% of cholesterol in the body is carried as LDL-C in the blood
  • Lipoproteins are essential for the transportation of cholesterol, which in turn is vital for the biosynthesis of bile acids, vitamin D, and steroid hormones
  • Dietary intake and endogenous hepatic production are the two primary sources of cholesterol
• Normal values for LDL-C

  • Optimal: <100 mg/dL or < 2.6 mmol/L
  • Near optimal/above optimal: 100-129 mg/dL or 2.6-3.3 mmol/L
  • Borderline high: 130-159 mg/dL or 3.4-4.1 mmol/L
  • High: 160-189 mg/dL or 3.1-4.9 mmol/L
  • Very high: >190 mg/dL or > 4.9 mmol/L
• Higher LDL-C value


  Associated with an increased risk for the development of CAD, and intervention may be needed
• High-Density Lipoprotein Cholesterol (HDL-C)

  • Produced and secreted by the liver and intestine
  • Acts as transporters for cholesterol from tissues to the liver
  • High levels of HDL-C are deemed desirable due to their inverse relation with coronary risk, hence HDL-C is commonly called "good cholesterol"
• Normal values for HDL-C

  • Low: <40 mg/dL
  • Optimal: >60 mg/dL
• Elevated HDL levels


  Associated with a decreased risk for cardiovascular diseases
• Decreased HDL levels


  Can be associated with recent illness, starvation, stress, smoking, obesity, lack of exercise, hypertriglyceridemia, or may be due to some medications (e.g., thiazide diuretics, steroids, beta blockers)
• Regular aerobic exercise, smoking cessation, a decrease in body mass index, and mild therapy with HMG-CoA reductase inhibitors

  Can help increase HDL levels
• High-Density Lipoprotein Cholesterol (HDL-C)

  • Produced and secreted by the liver and intestine
  • Acts as transporters for cholesterol from tissues to the liver
  • High levels are desirable due to inverse relation with coronary risk, hence called "good cholesterol"
• Normal HDL-C values


  • Low: <40 mg/dL
  • Optimal: >60 mg/dL