Lesson 6

• Diurnal variation


  Fluctuations in the levels of certain substances in the body over the course of a day
• Substances affected by diurnal variation

  • Cortisol
  • Adrenocorticotropic hormone
  • Plasma renin activity
  • Aldosterone
  • Insulin
  • Growth Hormone
  • Acid Phosphatase
  • Thyroxine
  • Prolactin
  • Iron
  • Calcium
• Cortisol


  • Peaks 4–6 AM; lowest 8 PM–12 AM; 50% lower at 8 PM than at 8 AM; increased with stress
• Adrenocorticotropic hormone


  • Lower at night; increased with stress
• Plasma renin activity


  • Lower at night; higher when standing than supine
• Aldosterone


  • Lower at night; release in adrenal glands
• Insulin


  • Lower at night; in diabetes
• Growth Hormone & Acid Phosphatase


  • Higher in afternoon and evening
• Thyroxine


  • Increases with exercise
• Prolactin


  • Higher with stress; higher levels at 4 and 8 AM and at 8 and 10 PM
• Iron


  • Peaks early to late morning; decreases up to 30% during the day
• Calcium


  • 4% decrease supine
• Effects of exercise


  • Increase in creatine kinase (CK), aspartate aminotransferase (AST), and lactate dehydrogenase (LD)
  • Increase in potassium
  • Increase in prolactin (in long-distance athletes)
  • Decrease in serum gonadotropins and sex steroid (in long-distance athletes)
• Effects of diet


  • Increase in ammonia, urea, and uric acid levels in high-protein diets
  • Increase in cortisol and ACTH levels with caffeine consumption
  • Increase in glucose levels with carbohydrate/sugar ingestion
  • Decrease in Hgb levels with excessive fluid intake
  • Electrolyte imbalance with excessive fluid intake
  • Increase in lipid levels with fatty food consumption
  • False positive stool occult blood test with certain food ingestion
  • Increase in TAG/TGY, liver enzymes, and liver function tests with chronic alcohol consumption
• Stress


  • Causes transient elevations in WBCs
  • Induces production of ACTH, cortisol, and catecholamines
• Posture


  • Upright position increases hydrostatic pressure, causing reduction of plasma volume and increased concentration of proteins
  • Change from supine to upright can cause up to 15% variation in total and HDL cholesterol
• Tourniquet application


  • May increase serum enzymes, proteins, and protein-bound substances
  • Prolonged application results in venous stasis (hemoconcentration)
• Age-related changes


  • Newborns have higher Hb F and bilirubin levels
  • Infants have lower glucose levels than adults
  • Alkaline phosphatase and creatinine increase with skeletal growth and muscle development
  • Elderly have decreased secretion of triiodothyronine, parathyroid hormone, aldosterone, and cortisol
  • Decrease in testosterone in men after age 50; increase in pituitary gonadotropins in women after age 50
  • WBC range differs between adults and children
  • Fetal Hb is higher in newborns, Hb A2 and A are higher in adults
• Gender differences


  • Men have higher alkaline phosphatase, aminotransferase, creatine kinase, and aldolase levels
  • Women have lower levels of magnesium, calcium, albumin, Hb, serum iron, and ferritin
• Tobacco smoking


  • Increases carboxyhemoglobin, Hb, RBC count, MCV, and WBC count
  • Decreases sperm count and motility
• Carboxyhemoglobin


  Complex of carbon monoxide and Hb, formed when carbon monoxide is inhaled and binds to Hb in RBCs
• Diabetes


  • Type 1 is juvenile diabetes, Type 2 occurs in adulthood
  • Insulin tries to facilitate glucose entry into cells, but can lead to cells becoming immune to insulin
  • Hyperglycemia and hypoglycemia can occur
• Hemolysis


  • Serum/plasma layer is pink or red
  • Falsely increases potassium, magnesium, iron, lactate dehydrogenase, phosphorus, ammonium, and total protein
• Alcohol ingestion


  • Increases uric acid, triglycerides, and gamma glutamyltransferase
  • Causes hypoglycemia and hyperglycemia
• Dehydration


  • Affects RBCs, enzymes, iron, calcium, sodium, and coagulation factors
  • Can cause hemoconcentration
• Drug therapy


  • Chemotherapy decreases blood cells, especially WBCs and platelets
  • Liver-toxic drugs increase liver enzymes and decrease clotting factors
• Serum is pink or red
• Falsely increased in Hemolysis

  • Potassium
  • Magnesium
  • Iron
  • Lactate dehydrogenase
  • Phosphorus
  • Ammonium
  • Total protein
• Potassium


  Intracellular electrolyte
• Normally platelets release potassium during clotting
• Serum has a slightly higher value of potassium than plasma
• Substances increased by alcohol ingestion

  • Uric acid
  • Triglycerides
  • Gamma glutamyltransferase (GGT)
• Alcohol ingestion causes hypoglycemia
• Hyperglycemia


  Cells become saturated with insulin
• Hypoglycemia


  Cells accept more glucose inside
• Hypoglycemia results in low glucose in plasma
• Blood components affected by dehydration

  • RBCs
  • Enzymes
  • Iron
  • Calcium
  • Sodium
  • Coagulation factors
• Dehydration can cause hemoconcentration
• Effects of chemotherapy drugs

  • Decrease in blood cells, especially WBCs and platelets
• Many drugs are toxic to the liver, increasing levels of liver enzymes such as ALT, AST, LD and decreasing production of clotting factors