Thyroid and Diabetic Testing Lecture Powerpoint Flashcards
Populations to screen for diabetes (6)
- Asymptomatic adults age 45+
- all individuals with risk factors (obese, family history)
- minority
- PCOS
- low HDL, high triglycerides
- recurrent yeast infections
HbA1C scale for diabetes
<5.7% healthy
5.7-6.4% prediabetic
>6.5% diagnostic** for diabetes
Fasting plasma glucose scale for diabetes
- 70-100mg/dL normal
- 100-126mg/dL prediabetes
- > 126mg/dL diabetes
Screening guidelines for diabetes
-symptomatic presentation (polyuria, polydipsia, weight loss) AND casual plasma glucose >200mg/dL
Fasting plasma glucose follows a ___ hour fast
8
Some conditions that can lead to elevated fasting glucose (5)
- Lab error
- corticosteroids
- excess glucagon
- B blockers
- caffeine or other drugs
Random glucose test
Done without fast, should never be >200mg/dL otherwise strongly indicative of diabetes (casual, indicates need for further testing)
Glucose Tolerance Test and what is it particularly useful in diagnosing?
- Only performed in patients who have been on unrestricted diet/physical activity for 3 days before testing, involves administration of 50-100g oral glucose administered after 10 hour fast
- Gestational diabetes
Goal of diabetic control is to limit…
….microvascular and macrovascular end organ damage
Common microvascular complications of diabetes (3) and common macrovascular ones (3)
- eye (cataracts and glaucoma)
- kidney (nephropathy)
- neuropathy
- brain (stroke)
- heart (CAD)
- extremities (peripheral vascular disease)
HbA1C testing
Measures 70% of glycosylated hemoglobin in blood which remains for the 120 day lifespan of the RBC (avg) (does not reflect acute increase or decrease) and therefore allows for highly accurate measure of blood glucose conc.
__% change in A1C reflects a change of about ___mg/dL in avg blood glucose
1, 30
Conditions that alter HbA1C (4)
- Iron deficiency (increased)
- sickle cell (decreased)
- bleeding (decreased)
- toxicity (increased)
Creatinine levels and diabetes
Increased suggest presence of diabetes, low is not common and not a concern unless pregnant when it should be lower (if not then cause for concern)
Microalbumin and microalbumin/creatinine ratio (and what should healthy value be?)
- Microalbumin test is an early indicator of kidney failure (albumin produced in liver and should not be present in blood when kidneys functioning properly) requiring 24 hour urine collection
- Microalbumin creatinine ratio is close to a 24 hour microalbumin test regarding accuracy without requiring 24 hour collection and is thus preferred (<30:1 ratio)
How often is microalbumin/creatinine ratio ordered in diabetic patients?
Annually
Magnesium levels in diabetic patients
-often decreased, low levels accentuate insulin resistance and exacerbate the cardiovascular risks
When is an insulin levels ordered? (3)
- evaluate PCOS
- diagnose insulinoma
- Determine cause of hypoglycemia (order alongside c peptide to monitor endogenous insulin levels)
Conditions with elevated insulin levels (4)
- cushing syndrome
- drug causes such as corticosteroids, levodopa, contraceptives
- obesity
- early type 2 diabetes
Conditions with decreased insulin levels (2)
- type 1 diabetes and late stage type 2
- hypopituitarism
Why order a c peptide level in suspected diabetic patient?
Monitor insulin production by the B cells of the pancreas to determine the cause of hypoglycemia - see if body producing enough of own insulin and are insulin resistant or not
C peptide levels in type 1 vs type 2 diabetics
C peptide level will be zero in type 1 diabetics (not producing insulin), in type 2 if left uncontrolled over time will drop to zero
Actions of thyroid hormone (6)
- Increase body’s metabolic rate and O2 consumption
- calorigenic effect increasing heat production
- increase heart rate and contraction strength
- increase respiratory rate
- stimulate appetite and breakdown of carbs, fats, proteins
- turn on and off various nuclear receptors
What do the C cells (parafollicular cells) of the thyroid produce?
Calcitonin
Why is T3 more metabolically active than T4?
T3 has a much shorter half life and composes the majority in the circulation while more T4 is stored in the gland itself (and thus takes longer to reach a steady state in artificial replacement as well)
Synthroid and armour thyroid
Artificial T4 and T3 and T4 respectively (T3 alone not very useful because it has such a short half life requiring frequent dosing intervals)
Reverse T3 definition
Minorly biologically active thyroid hormone present in elderly that should never be ordered for a patient as a supplement
2 major plasma proteins that are responsible for transport of thyroid hormone
- Thyroid binding globulin
- Albumin
Only __ T3/4 can penetrate cellular membranes and exert biologic activity
Unbound
Test of choice for pituitary and hypothalamic thyroid function tests and its normal range
TSH assay (most specific and sensitive), .1-5 uU/MI
Primary hypothyroidism sees a ___ TSH, very low levels of TSH can suggest ___
elevated, hyperthyroidism
A TSH over ___ requires treatment
10 uU/MI
2 uses of serum thyroglobulin levels
- follow thyroid cancer patients post thyroidectomy to consider recurrence
- elevated if thyroid is source of hyperthyroidism, low if exogenous source (factitious vs exogenous sources)
ELISA T3/T4 test
Offers direct measurement of free hormone highly sensitive and specific, reasonably inexpensive and unaffected by thyroxin binding globulin levels
Causes of elevated serum T4 (4)
- graves disease
- toxic multinodular goiter
- toxic adenoma
- thyroiditis
Causes of decreased serum T4 (3)
- hypothyroidism
- amiodarone
- post partum transient toxicosis
Hyperthyroidism + antithyroid antibodies suggests…
Hypothyroidism + antithyroid antibodies suggests…
….Graves disease
….hashimoto’s thyroiditis
Radionuclide scanning thyroid imaging
-Use of an isotope of iodine to determine if a nodule is hyperactive or underactive based on how it takes up the iodine (almost all cancers and benign lesions are cold)
Test of choice for thyroid nodule workup
Fine needle biopsy
Thyroid ultrasonography
Used to determine dimensions of thyroid lobes or nodules to see if solid, cystic, or mixed, important for monitoring course
C peptide
A protein released in equal amounts alongside insulin into the bloodstream allowing it to be a marker of insulin production (endogenous, not present with exogenous) and release in the body
2 standard tests to get when assessing thyroid and one to order when findings are abnormal
- TSH
- Free T4
- Free T3
