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
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