Endocrine and Cardiovascular Laboratory Values

Question 1

how is blood glucose tightly regulated?

Answer 1

– 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

Question 2

common tests for blood glucose

Answer 2

Common tests include
– Random blood glucose
– Fasting blood glucose
– Oral Glucose Tolerance Test (blood glucose)
– Hemoglobin A1c

Question 3

Blood Glucose Tests

what are the randges for blood glucose and A1c?

Answer 3

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

Question 4

Clinical Implications of Blood Glucose Tests

Answer 4

• 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%

Question 5

Thyroid Hormones

- fxn?

Answer 5

• 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

Question 6

Thyroid Hormone Laboratory Values

Answer 6

• 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

Question 7

describe hypothyroidism

Answer 7

(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

Question 8

describe hyperthyroidism

Answer 8

(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

Question 9

Adrenal cortex
– Accounts for 90% of the gland
– Secretes 3 types of hormones

role of cortisol?

Answer 9

– 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

Question 10

Hypothalamic-Pituitary-Adrenal Axis

Answer 10

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

Question 11

Adrenal Function Laboratory Values

Answer 11

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

Question 12

signs and symptom of adrenal insuff.

Answer 12

• Weakness, lethargy, fatigue, anorexia, weight loss, hypoglycemia

Question 13

signs and symptom of adrenal excess.

Answer 13

• Increased body weight, redistribution of body fat (centripetal obesity), hypertension, hirsutism

regarless of evening or morning

Question 14

describe Addison’s Disease

Answer 14

AD INSUFF
Organ has problems itself (adrenal glands) - pituitary sensing low cortisol - release ACTH

• high ACTH, low cortisol

Question 15

describe hypopituitarism

Answer 15

AD INSUFF
Pituitary not functioning properly, not releasing ACTH

• low ACTH, low cortisol

Question 16

Cushing’s Disease

Answer 16

AD EXCESS
pituitary adenoma

• high ACTH, high cortisol

Question 17

Cushing’s Syndrome (adrenal adenoma)

Answer 17

AD EXCESS

- low ACTH, high cortisol

Question 18

Cushing’s Syndrome (excess exogenous glucocorticoid use)

Answer 18

AD EXCESS

• low ACTH, low cortisol
• if exogenous glucocorticoid is suddenly stopped, this can cause adrenal insufficiency (hypopituitarism)

Question 19

Therapeutic Monitoring for adrenal conditions

- which lab tests?

Answer 19

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

Question 20

what are the 3 major lipids and what do they do

Answer 20

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)

Question 21

how are lipids transported?

Answer 21

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

Question 22

three major categories of lipoproteins (based on density of the particle)?

Answer 22

– 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

Question 23

A lipid panel reports blood levels for 5 things

Answer 23

– 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

Question 24

see lipid lab values slide 24

Answer 24

ok

Question 25

the heart has which 2 basic properties?

what happens when the heart is damaged?

Answer 25

– 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

Question 26

Cardiac Injury Laboratory Values
which cardiac proteins?
which cardiac enzyme?

Answer 26

• Cardiac proteins
– Troponin I (TnI) <0.12 mcg/L
– Troponin T (TnT) <0.01 mcg/L
• Cardiac enzyme
– Creatine kinase MB <3 mcg/L

Question 27

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)

Answer 27

• 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

Question 28

coagulation

When a blood vessel is damaged, chemical mediators are released, which two important
processes are activated?

Answer 28

• 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

Question 29

Platelets

aka?
how are they removed?

Answer 29

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

Question 30

define the 2 platelet conditions

Answer 30

• 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

Question 31

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

Answer 31

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

Question 32

how to calculate International Normalized Ratio?

Answer 32

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

Question 33

Partial Thromboplastin Time

what does it measure?

Answer 33

• 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)

Question 34

Coagulation Conditions

Answer 34

• Vitamin K deficiencies
– Malnutrition
– Fat malabsorption (↓ absorption of vitamin K)
– Anticoagulants (warfarin)
• Drug interactions (with warfarin)