Diurnal Variations in Hormones and Physiology

Study Notes

Diurnal Variation

Cortisol peaks between 4-6 AM and is 50% lower at 8 PM
Adrenocorticotropic hormone (ACTH) is lower at night and increases with stress
Plasma renin activity is lower at night and higher when standing than supine
Aldosterone is lower at night
Insulin is lower at night
Growth hormone and acid phosphatase are higher in the afternoon and evening
Thyroxine increases with exercise
Prolactin peaks early to late morning, decreases up to 30% during the day
Iron levels decrease up to 30% during the day
Calcium levels decrease by 4% when supine

Exercise

Exercise increases lactic acid, creatine, protein, CK, AST, LDH, and potassium levels
Prolactin levels increase in long-distance athletes
Exercise decreases cholesterol, TAG/TGY, serum gonadotropin, and sex steroid levels in long-distance athletes

Diet

High-protein diets elevate ammonia, urea, and uric acid levels
Caffeine consumption increases cortisol and ACTH levels
Carbohydrate and sugar intake increases glucose levels
Drinking excessive amounts of water and other fluids decreases Hgb levels and causes electrolyte imbalance
Ingestion of foods like butter, margarine, cheese, cream, and some enteral preparations increases lipid levels
Meat, fish, iron, and horseradish consumption can lead to false positive stool occult blood test results

Stress

Emotional stress causes transient elevations in WBCs
Mental and physical stress induce ACTH, cortisol, and catecholamine production

Posture

Upright position reduces plasma volume and increases protein concentration
Albumin and calcium levels increase when changing from supine to upright position
Changing from lying to standing can cause up to a 15% variation in total and HDL cholesterol results

Tourniquet Application

Application increases serum enzymes, proteins, and protein-bound substances like cholesterol, calcium, and triglycerides
Prolonged application leads to venous stasis and anaerobiosis

Tobacco Smoke

Smoking increases cholesterol, cortisol, glucose, growth hormone, and triglyceride levels
Chronic smoking leads to decreased pulmonary function and increased RBC counts and hemoglobin levels

Ethanol Consumption

Increases plasma concentrations of lactate, urate, acetate, and acetaldehyde
Increases GGT concentration and mean erythrocyte volume
Causes hypoglycemia

Hemolysis

Increases potassium, ammonia, iron, and enzyme levels like AST, ALT, LDH, ALP, and CK

Age

RBC and WBC values are higher in newborns than in adults
Kidney function decreases with age

Altitude

RBC counts and related determinations like hemoglobin and hematocrit have higher reference ranges at higher altitudes

Dehydration

Affects blood components like RBCs, enzymes, iron, calcium, sodium, and coagulation factors
Difficult to obtain blood specimens from dehydrated patients

Drug Therapy

Chemotherapy drugs decrease blood cells, especially WBCs and platelets
Many drugs are toxic to the liver, increasing liver enzymes like ALT, AST, LDH, and decreasing clotting factors

Vascular Access

Arterial line: a catheter placed in an artery, usually radial, for continuous blood pressure measurement and blood collection
Arteriovenous shunt, fistula, or graft: a permanent surgical connection of an artery and vein for hemodialysis

Description

This quiz covers the daily fluctuations in hormones and physiological processes, including cortisol, adrenocorticotropic hormone, and more. Test your knowledge of how these factors change throughout the day.