Endocrine and Cardiovascular Laboratory Values Flashcards
how is blood glucose tightly regulated?
– Dietary consumption (carbohydrates)
– Endocrine hormones (insulin, glucagon)
– Cell membrane receptors (GLUT4)
• Used to identify people with diabetes and to follow response to antihyperglycemic drug therapy
common tests for blood glucose
Common tests include – Random blood glucose – Fasting blood glucose – Oral Glucose Tolerance Test (blood glucose) – Hemoglobin A1c
Blood Glucose Tests
what are the randges for blood glucose and A1c?
Blood glucose
– Reference Range
Random 3.3 – 11.0 mmol/L (regardless when person ate)
Fasting 3.3 – 6.0 mmol/L (not eaten for 8 hours)
– Critical Values
<2.0 mmol/L (hypoglycemic event)
>24.9 mmol/L (metabolic acidosis)
• Hemoglobin A1c (avg blood glucose over 3 months)
– Reference Range 4.3% – 5.9%
– Critical Values – none reported
- below 6% is normal
Clinical Implications of Blood Glucose Tests
• Random Blood Glucose: sample taken during a non-fasting state
– Should be <11.1 mmol/L
• Fasting Blood Glucose: no food consumed in the previous 8 hours
– Should be <7.0 mmol/L
• Oral Glucose Tolerance Test: sample taken 2 hours after a 75 gm glucose load
– Should be <11.1 mmol/L
• Hemoglobin A1c: glycated protein, indicates level of blood glucose control over the previous 2-3 months
– Should be <7.0%
Thyroid Hormones
- fxn?
• Regulate the body’s metabolism • Thyroid hormones – Tetraiodothyronine (T4) is more common - (T4 is converted in thyroid and peripherally to T3) – Triiodothyronine (T3) is more potent – Often used to assess hyperthyroidism • Thyroid Stimulating Hormone (TSH) – Regulates release of T3 and T4 from the thyroid – Present in systemic circulation – Used to monitor thyroid function
Thyroid Hormone Laboratory Values
• Thyroid Stimulating Hormone (TSH) – Reference Range 0.2-4.0 mU/L* • Tetraiodothyronine (T4 or thyroxine) – 99.9% protein bound ⟹ measure free T4 – Reference Range 10-26 pmol/L† • Triiodothyronine (T3) – 99.6% protein bound ⟹ measure free T3 – Reference Range 4.0-7.4 pmol/L† • Some drugs (lithium, amiodarone -> hyper/hypothyroidism, propranolol, corticosteroids, oral contraceptives, phenytoin, carbamazepine) can affect thyroid function and interfere with laboratory tests
- not practical to sample TRH as it is only in that part of brain
T3 much shorter half life, hard to measure
describe hypothyroidism
(reduced thyroid function)
– Consider signs and symptoms of the patient
• Weight gain, dry skin, fatigue, cold intolerance, constipation, menstrual irregularities
– Thyroid Stimulating Hormone (TSH) > 4.0 mu/L
– Free T4 < 10 pmol/L
describe hyperthyroidism
(excessive thyroid function)
– Consider signs and symptoms of the patient
• Weight loss, palpitations, tremor, sweating, heat intolerance, nervousness, muscular weakness, usually goiter is present
– Thyroid Stimulating Hormone (TSH) <0.2 mU/L (very low almost unmeasurable)
– Free T4 >26 pmol/L
Adrenal cortex
– Accounts for 90% of the gland
– Secretes 3 types of hormones
role of cortisol?
– Regulates enzyme levels for metabolism
– May act to limit inflammation and immune
responses
– Permissive role in blood pressure maintenance
– Stress stimulates secretion above basal levels
Hypothalamic-Pituitary-Adrenal Axis
hypothalamus releases cortioctropic releasing hormone
- ant pit releases ACTH
- adrenal cortex releases cortisol which gives neg feedback and acts on target cells
- Plasma ACTH and Glucocorticoid Levels at Different
Timepoints During the Day
Adrenal Function Laboratory Values
Adrenocorticotropic Hormone (ACTH)
– Reference Range*
• Morning <18 pmol/L (<80 pg/mL)
• Evening <11 pmol/L (<50 pg/mL)
Cortisol – Reference Range (Blood)* • Morning 138-635 nmol/L • Afternoon 83-441 nmol/L – Reference Range (Urine)* • 24 hour urine collection <276 nmol • Some drugs (corticosteroids, estrogen, spironoloactone) and some conditions (being pregnant, having a severe injury, physical or emotional stress) caninfluence the laboratory test
signs and symptom of adrenal insuff.
• Weakness, lethargy, fatigue, anorexia, weight loss, hypoglycemia
signs and symptom of adrenal excess.
• Increased body weight, redistribution of body fat (centripetal obesity), hypertension, hirsutism
regarless of evening or morning
describe Addison’s Disease
AD INSUFF
Organ has problems itself (adrenal glands) - pituitary sensing low cortisol - release ACTH
- high ACTH, low cortisol
describe hypopituitarism
AD INSUFF
Pituitary not functioning properly, not releasing ACTH
- low ACTH, low cortisol
Cushing’s Disease
AD EXCESS
pituitary adenoma
- high ACTH, high cortisol
Cushing’s Syndrome (adrenal adenoma)
AD EXCESS
- low ACTH, high cortisol
Cushing’s Syndrome (excess exogenous glucocorticoid use)
AD EXCESS
- low ACTH, low cortisol
- if exogenous glucocorticoid is suddenly stopped, this can cause adrenal insufficiency (hypopituitarism)
Therapeutic Monitoring for adrenal conditions
- which lab tests?
Management of adrenal conditions ⟹ HPA axis lecture later in the course
• Laboratory tests used to monitor therapy
– None
– Generally used to diagnose the condition and identify the cause
– Generally follow symptoms of the patient to adjust therapy
what are the 3 major lipids and what do they do
Cholesterol is a major building resource for
the body (cell membranes, hormones)
– Excessive amounts of cholesterol in the blood
can increase the risk of heart disease
• Atherosclerosis: accumulation of fats, cholesterol,
and other substances in the wall of an artery
Triglycerides are used as a source of
energy (primarily in muscles)
Phospholipids are a major component of all cell membranes (bilayer)
how are lipids transported?
in the blood within lipoproteins (complex, spherical particles)
– Surface is composed of phospholipid, proteins, and free cholesterol
– Core is composed of triglycerides and cholesterol esters
three major categories of lipoproteins (based on density of the particle)?
– High-density lipoprotein (HDL): helps remove cholesterol from the body (”good cholesterol”)
– Low-density lipoprotein (LDL): carries mostly fat and a small amount of protein, moves cholesterol from the liver to other parts of the body (“bad cholesterol”)
– Very low-density lipoprotein (VLDL): contains very little protein, mainly moves triglycerides away from the liver to other parts of the body
A lipid panel reports blood levels for 5 things
– Total Cholesterol: the sum of all cholesterol (includes HDL, LDL, and VLDL) – High-density lipoprotein (HDL) – Low-density lipoprotein (LDL) – HDL/Total Ratio – Triglycerides
Fasting before the blood sample is drawn (no food or drink for 9 to
12 hours) is sometimes requested
– e.g., if triglyceride levels are >4.5 mmol/L
see lipid lab values slide 24
ok
the heart has which 2 basic properties?
what happens when the heart is damaged?
– Electrical
– Mechanical
• These two properties work in a coordinated fashion to pump blood to the lungs (right side heart) and body tissues (left side of heart)
When the heart is damaged,
– Electrical conduction changes can be detected on an electrocardiogram
– Mechanical function changes can be measured through a variety of tests (e.g., echocardiography)
– Enzymes and proteins are released into the blood
Cardiac Injury Laboratory Values
which cardiac proteins?
which cardiac enzyme?
• Cardiac proteins – Troponin I (TnI) <0.12 mcg/L – Troponin T (TnT) <0.01 mcg/L • Cardiac enzyme – Creatine kinase MB <3 mcg/L
what is creatine kinase?
what causes CK level increase (3
• Total Creatine Kinase
– Reference Range* 38-174 U/L (men)
26-140 U/L (women)
• Enzyme present in other tissues, identified by the fractional unit
– BB Brain
– MB Cardiac tissue
– MM Cardiac and skeletal muscle
• Causes of CK level increases
– Skeletal muscle (e.g., vigorous exercise, trauma, rhabdomyolysis)
– Cardiac muscle (e.g., myocarditis, acute myocardial infarction)
– Medications: “statins”, fibrates, ethanol (binge drinking), intramuscular injections
coagulation
When a blood vessel is damaged, chemical mediators are released, which two important
processes are activated?
• Platelet Activation: platelets swell and create pseudopods, clump together, and form a plug
• Fibrin Formation: clotting factors released by platelets and other cells create a fibrin matrix
that stabilizes the plug and produces an insoluble clot
Platelets
aka?
how are they removed?
thrombocytes are formed in the extravascular spaces of bone marrow
• Average lifespan is 8-12 days
• Removed from circulation by the spleen, liver, and bone marrow
• Reference Range 140-400 x 109/L
define the 2 platelet conditions
• Platelet Conditions
– Thrombocytosis (elevated platelet count): bleeding, iron deficiency, some cancers, problems with bone marrow, splenectomy, trauma
– Thrombocytopenia (decreased platelet count): adverse drug effects, liver disease, thrombocytopenia purpura
Prothrombin Time measures?
• Wide variation in lab-specific reagents and instruments used to measure PT
– Reference range varies from lab to lab
⟹Most labs will now only report the INR
long it takes (in seconds) for blood to clot in the presence of sufficient concentration of calcium and tissue thromboplastin
– Coagulation is activated through the extrinsic pathway
• Prothrombin (Factor II) is one of several vitamin K-dependent clotting factors made by the liver
– Indirectly, the PT will help assess liver function
– Was mainly used to monitor warfarin therapy
how to calculate International Normalized Ratio?
INR = PTPatient ÷ PTControl
- Control Prothrombin Time: is standardized for the potency of the thromboplastin reagent developed by the World Health Organization
- Reference Range* 0.8-1.2
Partial Thromboplastin Time
what does it measure?
• Used to monitor the effects of unfractionated heparin
• Measures how long it takes (in seconds) for blood to clot
– Coagulation is activated through the intrinsic pathway (excludes factors VII [tissue factor] and XIII [fibrin stabilizing factor])
• An activated partial thromboplastin time (aPTT) includes the addition of an activator to accelerate the clotting time
• Reference Range* 60-70 seconds (PTT)
30-40 seconds (aPTT)
Coagulation Conditions
• Vitamin K deficiencies – Malnutrition – Fat malabsorption (↓ absorption of vitamin K) – Anticoagulants (warfarin) • Drug interactions (with warfarin)
