Endocrine labs Flashcards by Daniel Kruger

Diabetes Mellitus, What types? What are they specific to?

Type I

Usual onset under the age of 30
Autoimmune destruction of the pancreatic islet B cells
Insulin dependent

Type II

Most common endocrine disorder in the US
Tissue insensitivity to insulin
Obesity and adult onset

Gestational Diabetes

30-50% change of developing type 2 diabetes later.

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What is glucose used to screen for?

Glucose is used to screen for diabetes

Usually is measured fasting, and then a 2 hour post prandial test

pearl- if glucose is abnormal, - first assess if it was a fasting or non fasting glucose.

fasting should not include coffee or additives - no caffeine. Water and medications only.

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What is the best indicator for glucose homeostasis?

Fasting glucose.

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Fasting Glucose parameters and facts. what is a normal fasting glucose? What fasting glucose indicates diabetes?

Fasting glucose is the best indicator for glucose homeostasis
It may be used to monitor therapy in diabetics
Normal fasting glucose is considered less than 110.
- there is lab to lab variation though
Fasting glucose of greater than 110 and less than 126 is pre-diabetes
- also called impaired fasting glucose
Fasting glucose greater than 126 on 2 seperate occasions is diagnostic for diabetes.

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What is the 2 hour post prandial glucose test?

a 2 hour post prandial glucose test measures glucose 2 hours after a meal
Meal acts as glucose challenge
- insulin normally secreted after a meal, glucose should return to premeal rane in 2 hours
- Diabetes- glucose level remains elevated at 2 hours
Normal <140mg/dl
- If greater than 200 mg/dl - confirms diagnosis of diabetes
- If 140-200mg/dl follow with glucose tolerance test.

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What is the glucose tolerance test? when would you use it?

The glucose tolerance test is usually a 2-3 hour test some people still do 4 hours
When to order
- pregnancy/women with history of large birth weights or stillborns
- abnormal 2 hour post prandial glucose, not diagnostic of diabetes (140-200)
- Obese patients
- History of recurrent infections
- Patients with delayed healing of wounds.

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What are the normal results for a glucose tolerance test? what is diagnostic of diabetes?

Normal
- fasting <110mg/dl
- 1 hour <200
- 2 Hour <140
- 3 hour 70-115mg/dl
Criteria for diagnosis of diabetes
- Fasting glucose is greater than 126 mg/dl
- 2 hour glucose > 200mg/dl

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What are other factors that can affect glucose levels?

Stress - releases cortisol which acts to increase glucose via gluconeogensis and glycogenolysis. It also decreeases glycogenesis.
Caffeine can elevate glucose
IV fluids containing dextrose - do not give dextrose containing fluids to diabetic patients
pregnancy
durgs - prednisone, and estrogens
smoking

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What patient education is needed prior to glucose testing?

You should be fasting for 8-12 hours
Do not smoke during glucose tolerance test - this can elevate glucose and give an inaccurate reading
Do not exercise 24 hours before the glucose tolerance test.

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What is Glycosylated Hemoglobin? what does it tell you? What is a nomral range?

Glycosylated Hemoglobin is HGA1c. It tells you the measurement of glucose levels over the last 3 month period.

Red blood cells contian HgA1c and binds strongly to glucose

120 day lifespan of RBC gives us a 3-4 month average of what their glucose levels have been. This is indicative of glucose control.

Normal levels 4-5.7%. Greater than 6.5% is considered poor control but there is some debate to this.
Fasting is not required for this test.

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A1c results for normal, prediabetics, diabetics.

Normal less than 5.7%
pre diabetic 5.7%-6.4%
Diabetic - 6.5% or higher.

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What are the diagnostic criteria for diabetes?

A1c is greater than 6.5%

Fasting glucose is greater than 126 mg/dl or

Oral glucose tolerance test with 2 hour level at 200 mg/dl or higher.

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What is ketoacidosis?

Ketoacidosis is a diabetic emergency
Type 1 diabetes is most common and starting to see it in some type ii diabetics.
Basically it is an insulin deficiency resulting in protein breakdown and increased hepatic production of glucose
Lipolysis occurs and free fatty acids are converted to ketone bodies (beta-hydroxybutyric acid and acetoacetic acid)
- This results in metabolic acidosis because the ketones are acidic
- Presents with dehydration, lethargy, acetone smelling breath, occasionally a coma.

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What are the lab fidings in ketoacidosis?

Glucose is greater than 300 mg/dl
Low bicarbonate (0-15mEq/L)
Low pH (lower than 7.2)
Na and K levels may be low, normal or high. Depends on what phase they are in.

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How is potassium affected in ketoacidosis?

Initially, insluin deficiency usualyl causes elevated potassium levels due to extracellular movement of potassium. intracellular to extracellular
Hypertonicity and acidosis cause K to move from intraacellular to extracellular space
Total K depletion occurs the longer ketoacidosis progresses - results in cardiac dysrythmia
Pearl- inital treatment of ketoacidosis includes insulsin administartion with potassium
1. This is because there is a potassium depletion
2. but mainly because potassium will help insulin go into the cell.

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What are the UA tests of someone with ketoacidosis?

Ketones are present on urinalysis
Urine ketone test
- Detects acetoacetic acid
- Unable to detect beta-hydroxybutyrate
  - Can only detect one ketone
    - bottom line is they could be in ketoacidosis and have a negative urine ketone test.

Other than a1c and glucose levels, what are other tests used to monitor diabetics?

Urine protein is a common test to run
- Part of a routine urinalysis
- shows kidney damage
- If negative, follow with microalbumin urine test
  - this is a more senstive test that predicts glomerular damage sooner
- Microalbuminuria = glomerular damage, predictive of nephropathy
- Other causes of microalbuminuria
  - exercise, hypertension, UTI, heart failure and fever
We can also test for lipids
- LDL and HDL

what is urine Microalbumin?

Refers to albumin concentration in urine that is greater than normal but not enough to detect in routine urinalysis
Normal is less than 20mg/L, MA/Creat 0-3mg/g
Normally filtered and reabsorbed through glomeruli- diabetes cause glomerular permeability to exceed reabsorption
Related to duration of diagnosis and glycemic control
Screen at least annually in diabetics.

This can also be affected by hydration status. Correct for hyratoin status by utilizing (urine microalbumin/urine creatinine) x 1000.

What are the AHA guidelines for metabolic syndrome?

Elevated waist circumfrence
- men - equal to or great than 40 inches (102 cm)
- women - equal to or great than 35 inches (88cm)
Elevated triglycerides: euql to or greater than 150mg/dL
Reduced HDL
- men less than 40
- women less than 50
Elevated blood pressure: equal to or greater than 130/85 mm Hg or use of medication for hypertension
Elevated fasting glucose: Equal to or great than 100mg/dL or use of medciation for hyperglycemia

What does Thyroid Hormone do?

Regulates basal metabolic rate
Can affect protein, carbohydrate, and lipid metabolism
Synthesis depends on iodine (refer to physiology notes and text)
Thyroxine (t4) and triiodothyronine (t3) circulate in the serum bound to proteins (albumin)
Small amount of unbound (0.02% T4 and 0.2% T3) = free and available to tissues.
- Readily available, doesn’t rely on albumin to carry it around.
Secretion of thyroid is regulated by negative feedback system
Release of T4 and T3 is regulated by TSH - thyroid stimultating hormoen
- TSH is secretd by the anterior pituitary
  *

What are disorders of the thyroid?

Hypothyroidism

Underactive
Deficiency of T4 - thyroxine
High TSH - more sensitive lab marker so this is usually measured.

Hyperthyroidism

overactive
excessive T4
Low TSH

After, if TSH is abnormal measure free T4

TSH lab marker. What does it measure? what is its function

Measures the integretity of the hypothalamic pituitary-thyroid axis
Normal range varies between (0.4-5.0) Even @ high or low ranges, might not be a bad idea to screen for T4
Functions
- Initial screen for thyroid disorders
  - elevated =hypothyroid
  - decreased =hyperthyroid
- Also used to monitor therapy.

Free T4 lab marker, what does it do, what is it used for.

Measures unbound T4
Most accurate measurement of thyroid status, but not the most sensitive -TSH is most sensitive
Low = hypothyroidism
High = hyperthyroidism.

T3 lab marker, what does it do, what is it used for?

Not used as much
But used primarily to diagnose hyperthyroidism
T3 uptake
- indirectly estimates number of binding sites of thyroid bound by T3
- Indirect measure of T4
- Elevated = hyperthyroidism
- decreased= hypothyroidism.

What are non thyroid labs that you can use in thyroid disorder, are they increased or decreaed? What is a major contribution to new onset a fib?

* Hgb/Hct - can show anemia in thyroid disorders * Glucose - can be off in thyroid disorders * Both of these are usually decreased in the settings of thyroid disorders * Hyperthyroidism * Major contribution of new onset a fib.

What does the Parathyroid do? What is the most common cause hypercalcemia?

* Parathyroid is responsbile for calcium metabolism * Parathyroid hormoen is most important regulator of plasma calcium * Hypercalcemia relatively common * Most common cause is primary hyperparathyroidism * usually adenoma of the parathyroid gland.

What is calcium responsible for? How does it move in the blood?

* Calcium is necessary for many metabolic enzymatic pathways- cardiac function, neural trasnmission, and blood clotting * It moves in the blood 1/2 bound by albumin, and 1/2 free ionized calcium * If albmin is low, calcium is low * correction * normal albumin (4)-patient albumin)x 0.8 + Ca

What does the adrenal medulla secrete, what do the 3 layers of the adrenal cortex secrete?

The adrenal Medulla secretes catecholamines * norepinephrine and epinephrien The adrenal cortex is divided in to 3 layers and each layer secretes a different hormone * zona glomerulosa - Secretes mineralcorticoids such as aldosterone. * Zona fasciculata - Secretes glucocorticoids, such as cortisol * cortisol regulates fat, carbohydrate, and protein metabolism * zona reticularis - secretes androgens (sex hormones) * specifiaclly DHEA - an intermediate for sex hormones such as estrogen, DHT and testosterone.

What does Cortisol do? When is it highest and lowest?

* Cortisol helps regulate fat, carbohydrate and protein metabolism * Cortisol is secreted from the zona glomerulosa, whenever ACTH is released form the anterior pituitary. ACTH is released in response to CRH from the hypothalamus. * The hypothalamus secretes CRH depending on feedback from cortisol, time of day, and stress * Stress increases cortisol levels. * It has a diurnal variation * highest around 6-8am and lowest at midnight * routinely measured at 8 am and 4pm * Cortisol affects all cells * by stimulatiion of protein catabolism (occurs in all cells except hepatocytes * It also affects adipose connective tissue * increases lipolysis * decreases lipogenesis * Affects the liver * increases gluconeogenesis and glycogenolysis * decreases glycogenesis * This effectively increases glucose levels. * It also affects glucose levesl by inhibiting the effects of insuli * High doses of cortisol * increase retention of sodium, water, * decrease inflammation * suppress the immune system * inhibit connective tissue repair. * This has a negative feedback on the hypothalamus and anterior pituitary from releasing more ACTH and CRH.

What is cushings syndrome?

* cushing syndrome * excessive cortisol * hypertension, buffalo hump, moon faces * To Dx * test cortisol in the AM and PM * do a 24 hour urine cortisol tset * Do a dexamethasone suppression tset - suppress ACTH production * Primary - cortisol producing tumor - adrenal adenoma * ACTH producting tumors (cushings disease) * pituitary adenoma * ACTH stimulates coritisol production

Addisons' disease

* Adrenal insufficiency * Not producing enough cortisol or enough mineralcorticoids * It is an autoimmune attack * Decrease in cortisol levels * Get weakness, weight loss, increased pigmentaiton, hypotension and dizziness * To dx * Cosyntropin stimulatin test - * synthetic ACTH is given then cortisol levels are drawn at the time of injection, 30 minutes and 1 hour later. Cortisol greater than 20 is adequate response and isn't indicative of adrenal insufficiency *