CS2 Exam 1: Endocrine/STI/Cardio Testing

what is the normal value for a 2 y/o - adulthood for glucose?

70-110 mg/dL fasting, <200 mg/dL random

what is the critical value for glucose for children - adulthood?

<50 or >450 mg/dL

what conditions are glucose levels increased in (hyperglycemia)?

DM & endocrine disorders (glucagonoma, Cushing's, acromegaly)

what conditions are glucose levels decreased in?

DM meds (insulin) & endocrine disorders (insulinoma & Addison's)

what are the 3 ways to capture someone's glucose in real time?

venipuncture, capillary glucose measurement, & minimally invasive/continuous glucose monitoring (CGM)

what are the diagnostic criteria for DM with a venous sample collection?

>126 mg/dL (IFG is 100-125)

when is CGM indicated?

for anyone on an intensive insulin regimen (ex. >3 injections per day, T1DM, pregnancy w/ diabetes) or anyone with problematic hypoglycemia

what is a hallmark feature of T2DM & GDM?

IR

what are the types of oral glucose tolerance tests?

O'Sullivan test, postprandial BG, & glucose tolerance test

how long should you fast for an oral glucose tolerance test?

12 hours

what is the procedure for oral glucose tolerance testing?

1. fasting BG drawn

2. glucose load given over 5 mins

3. repeat glucose level at appropriate interval

what is the O'Sullivan test?

1-hr test, non-fasting, 50-g glucose, for pregnant pts only

what is the postprandial test?

2-hr test, fasting, 75-g, best for non-pregnant pts

what is the glucose tolerance test?

3-hr test, fasting, 75-g (100-g for pregnancy), indicated if O'Sullivans was abnormal

what are the diagnostic criteria for fasting plasma glucose?

-normal: <100 mg/dL

-impaired: 100-125 mg/dL

-DM: ≥126 mg/dL

what is the diagnosis if the only abnormality is 100-125 mg/dL for fasting plasma glucose?

IFG

what are the diagnostic criteria for 2-hr postprandial glucose?

-normal: <140 mg/dL

-impaired: 140-199 mg/dL

-DM: ≥200 mg/dL

what can be used to both diagnose and monitor control of disease, and does NOT require fasting?

HbA1C

what is HbA1C?

HbA1C combines w/ glucose in blood to form glycohemoglobin (glycosylation) & reflects state of glycemia over preceding 8-12 weeks

how long do RBCs live?

~120 days

when should HbA1C measurements be checked?

every 3-4 months

what are the diagnostic criteria for HbA1C?

-normal: <5.7%

-impaired: 5.7-6.4% (prediabetes)

-DM: ≥6.5% (good control <7%)

what are the MPG values for a HbA1C value of 6 & 7?

135; 170 (increases by 35 linearly)

when is HbA1C contraindicated?

those w/ Hb variants, changes in RBC survival, & anemia of CKD

what is the renal (urinary) osmotic threshold for glucose?

180 mg/dL

what are ketones?

byproduct of fat catabolism

what are the 3 physiologic ketones produced by the human body?

-acetone

-acetate (acetoacetic acid)

-B-hydroxybuterate acid

what ketone is NOT assessed via dipstick urinalysis or Acetest tablets & is the predominant ketone in DKA?

B-HBA

what is included in the DM autoantibody panel?

insulin autoantibody, islet cell antibody, & glutamic acid decarboxylase 65 antibody

when is a DM autoantibody panel clinically used?

evaluating T1DM

what are some considerations for the autoantibody panel?

almost all pts receiving insulin will have +Ab, Ab can cause secondary IR, & immune-mediated insulin allergies can develop (IgE Ab)

what is fructosamine?

formed by glycosylation of albumin, clinically used when HbA1C is inaccurate

what has a much shorter half-life than Hb?

albumin (reflects state of glycemic control for only preceding 15-20 days)

what does an insulin assay assess?

circulating insulin in the body (endogenous production in pancreas and exogenously administered insulin)

when is an insulin assay clinically used?

work-up of fasting hypoglycemia or to diagnose insulinomas (compare insulin/glucose ratio, nL <3.0)

what interferes w/ an insulin assay?

insulin Ab & exogenous insulin

what do C-peptide assays assess?

endogenous production of proinsulin/insulin (insulin more accurate unless exogenous insulin administration or +IAA)

when is C-peptide clinically used?

distinguish T1DM & T2DM (most helpful at initial diagnosis) & workup of hypoglycemia (ddx insulinoma from factitious hypoglycemia)

what does no endogenous production of insulin mean?

no C-peptide

when are serum glucagon levels clinically used?

workup for glucagonoma

what is the typical lipoprotein pattern seen in pts w/ glucose dysregulation?

high TG, low HDL

what is the preferred method for screening a pt for early diabetic nephropathy?

UACR annually

what are nL (negative) results for UACR?

<30 mg/g

how is nephropathy diagnosed on UACR?

≥2 + results

what is the most common complication of DM?

neuropathy

what is the screening test for neuropathy?

diabetic foot exam w/ monofilament

what would lead to the diagnosis of proliferative vs non-proliferative retinopathy in a pt w/ retinopathy?

neovascularization

what common med is used in management of IR/T2DM?

metformin

what is the risk of metformin during a CT w/ contrast?

impaired renal clearance of contrast dye can lead to lactic acidosis (hold med for 48 hrs before, recheck BUN/Cr prior to restarting)

what type of acid-base disturbance results from DKA?

high anion gap metabolic acidosis

what is the respiratory compensation called for DKA?

Kussmaul's respirations

is a urine sample used to screen for DKA?

yes, but not used for formal diagnosis

what is Acetest?

blood sample to check for ketones in urine and blood (but does not assess for B-HBA)

what is the best way to assess for presence of ketosis?

serum osmolality assessment (B-HBA)

what conditions will serum osmolality be elevated in?

DKA, HHS, & LA

what are the axes of the anterior pituitary?

hypothalamic-pituitary-prolactin axis, growth hormone/insulin-like growth factor axis, & hypothalamic-pituitary-adrenocortical axis

what do primary disorders have dysfunction of?

end-organs ex. thyroid

what do secondary disorders of dysfunction of?

pituitary (central)

what do tertiary disorders have dysfunction of?

hypothalamus (central)

what are posterior pituitary disorders primarily related to?

ADH

what structure produces ADH?

hypothalamus

what is ectopic hormonal secretion?

production of a hormone by a cell/tissue type that does not normally produce that hormonal substance ex. ectopic ACTH/ADH secretion, PTHrP secretion

what is paraneoplastic syndrome?

patients w/ cancers manifest w/ sxs of hormone dysfx due to their tumor

how do you test hyposecretion disorders (ex. GH deficiency)?

stimulation testing

how do you test hypersecretion disorders (ex. GH excess)?

suppression testing

what is the natural physiological state of prolactin?

inhibition

what hormone functions as prolactin inhibitory hormone?

dopamine

when prolactin is secreted, it has a suppressive effect on which other neuroendocrine axis?

hypothalamic-pituitary-gonadal (HPG)

what do elevated levels of serum prolactin (PRL) lead to?

pituitary adenoma: prolactinoma

what is the diagnosis if sxs are galactorrhea after b/l tubal ligation, negative pregnancy test, intermittent HA, and some difficulty w/ peripheral vision?

prolactinoma (PRL-secreting pituitary tumor)

how would you diagnose a prolactinoma?

serum PRL level (high) & pituitary MRI (sella turcica)

when would CNS destructive disease elevate serum prolactin levels instead of decreasing them?

if it impairs the natural inhibitory mechanisms of PRL secretion

what do elevated levels of serum growth hormone (GH) lead to?

pituitary adenoma -> gigantism/acromegaly or Laron dwarfism

what do decreased levels of serum growth hormone (GH) lead to?

dwarfism

what is most likely the location of the neoplasm for patients w/ gigantism or acromegaly?

anterior pituitary

what tests would be used to diagnose gigantism or acromegaly?

serum IGF-1 levels (vs GH), GH suppression test, & pituitary MRI

what is the MC diagnostic study for GH suppression testing?

oral glucose tolerance testing (OGTT)

what blood test is preferred in the evaluation of possible growth related pathologies?

IGF-1 (provides most accurate reflection of mean plasma GH)

what do elevated levels of IGF-1 lead to?

pituitary adenoma -> gigantism/acromegaly

what do decreased levels of IGF-1 lead to?

dwarfism or Laron dwarfism

what lab changes would be expected in Laron dwarfism?

high GH, low IGF-1

which stimuli used during the workup of potential GH deficiency is most reliable but rarely used now due to significant risks/complications?

insulin

what do elevated levels of adrenocorticotropic hormone (ACTH) lead to?

Cushing disease, ectopic ACTH secretion, or primary adrenal failure

what do decreased levels of adrenocorticotropic hormone (ACTH) lead to?

another form of Cushing syndrome

what is serum cortisol?

glucocorticoid stress hormone that is highest from 6-8am

what do elevated levels of serum cortisol lead to?

Cushing syndrome (primary = adrenal, secondary = pituitary, or ectopic ACTH secretion)

what do decreased levels of serum cortisol lead to?

primary adrenal failure or pituitary destruction

what is considered the best way to assess cortisol levels?

24-hr urinary cortisol (but it doesn't tell you the etiology)

is salivary cortisol a convenient way to assess a patient for hypocortisolism?

no, used to assess hyperfunction and is collected at midnight

what assessment for Cushing syndrome helps determine etiology?

dexamethasone suppression testing (DST)

what is step 1 for rapid DST?

administer low dose 1mg test, if results are <5 mcg/dL stop here (this is nL) & if >10 move to step 2

what is step 2 for rapid DST?

administer high dose 8mg test and see if there is + or - suppression

what could be the etiologies of negative suppression (still high cortisol) after step 2?

adrenal hypersecretion (primary) of cortisol OR ectopic ACTH secretion

how are adrenal hypersecretion of cortisol and ectopic ACTH differentiated?

draw the ACTH level (low in adrenal disease, high in ectopic ACTH)

what testing is used for suspected hypocortisolism to determine the etiology?

cosyntropin stimulation testing

what do you need to take into consideration with cosyntropin stimulation testing?

make sure you treat adrenal crisis first

how can you differentiate primary (adrenal) vs secondary (pituitary) causes in the cosyntropin stimulation test?

draw baseline ACTH level before testing, if high it is primary & if low it is secondary

what is serum aldosterone?

mineralocorticoid regulated by the RAA pathway, secreted in response to ACTH

what is serum aldosterone used to diagnose?

hyperaldosteronism

what do elevated levels of serum aldosterone lead to?

-primary causes: adrenal adenoma or b/l adrenal hyperplasia

-secondary causes: high ACTH, RAA stimulation