Glucose Regulation, relevant hormones, and Diabetes Flashcards
What hormones are primarily responsible for decreasing blood glucose and for increasing it?
insulin and glucagon
What processes does glucagon stimulate and inhibit?
stimulates glycogenolysis and gluconeogenesis; inhibits glycolysis
name 3 secondary hormones that deliberately cause an increase in blood glucose levels; which two are insulin antagonists?
cortisol, epinephrine, and growth hormone. cortisol and growth hormone are insulin antagonists.
what does cortisol do?
regulates carb, fat & protein metabolism; water and electrolyte balance; suppresses inflammation ad allergic reactions
In what disease is cortisol elevated and has lost diurnal variation (meaning higher in morning)?
Cushing’s syndrome
differentiate between Cushing’s syndrome and Cushing’s Disease:
Syndrome: Body has made too much cortisol over a long period
Disease: pituitary tumor causing overproduction of cortisol; is cause of ~ 70% of Cushing’s Syndrome caused endogenously
What hormone regulates the release of cortisol? Where is cortisol and this stimulating hormone made?
ACTH: adrenal cortex (outer layer) and anterior pituitary
Describe in simple terms the pathway from gland to gland in production of cortisol
The hypothalamus produces corticotropin-releasing hormone (CRH) which stimulates the anterior pituitary to produce adrenal corticotropic hormone (ACTH); which stimulates the adrenal cortex to release cortisol
What are the 4 major adrenal hormones? which are made in the cortex and which in the medulla?
aldosterone, cortisol, and epinephrine and norepinephrine; The first two in the cortex, the latter two in the medulla
what are the catecholamines, their purpose, and their metabolites? Test specimens for each?
Epinephrine and norepinephrine; They stimulate the sympathetic nervous system in flight or flight syndrome; metabolites are metanephrines and VMA (vanillylmandelic acid); plasma and urine for catecholamines and metanephrine; urine for VMA
what does aldosterone do and where is it made?
Aldosterone’s primary function is to act on the late distal tubule and collecting duct of nephrons in the kidney, directly impacting sodium absorption and potassium excretion; made in adrenal cortex
describe in simple terms the renin-angiotensin-aldosterone-system
JG cells of kidney are stimulated by low BP or decreased sodium to produce renin–> renin in bloodstream activates angiotensinogen which is in plasma, coming from the liver–> now angiotensinogen is cleaved into Angiotensin I–> AT I gets converted by ACE in lungs or kidneys into AT II.
AT II binds various organs’ AT receptors (incl adrenal gland, brain, kidney, arterioles); net effect is sodium reabsorption and thus blood osmolarity increase, with increase in BP
List 10 things increases in uncontrolled Diabetes mellitus
Blood glucose, urine glucose, urine specific gravity, Osmolality of blood and urine, glycohemoglobin (A1C!!), and ketones;
Anion gap, BUN, , cholesterol, and trigs
what lab values are decreased in uncontrolled diabetes mellitus?
bicarbonate, and pH (more acidic)
what is considered positive for diabetes mellitus in a random plasma glucose reading?
> 200 mg/dL
what is considered diagnostic of diabetes mellitus with regards to fasting plasma glucose?
8 hours minimum fast; on greater than 2 occasions BG > 126 mg/dL
what is considered diagnostic of DM in regards to a 2-hour plasma glucose test given a 75 gram glucose load?
same as a random, > 200 mg/dL
WHat is the oral glucose tolerance test used to diagnose and what are the parameters of diagnosis?
gestational diabetes, done at 24 to 28 weeks; fasting, if > 92mg/dL ; 1 hour, > 180 ; 2-hr _>_153
what is the cutoff for A1C for diabetes diagnosis?
> 6.5%
what is the average reference range for normal fasting blood glucose?
70 to 99 mg/dL
How can the metabolism of blood glucose in specimens be prevented in order to not get a falsely lower reading? what changes are expected if blood is at room temperature?
chilling sample in ice water (slurry) or use of flouride in unseparated samples (it is a glycolytic inhibitor); Glucose levels fall by 2 to 3 % per hour at normal RT
common methods of analyzing blood glucose:
enzymatic using either glucose oxidase or hexokinase
what is the main form of lipid storage and what common methods are used to measure?
Triglycerides; enzymatic methods using lipase on fasting specimens
WHat can be measured in the urine of diabetics to help predict nephropathy? Why not just test albumin?
microalbumin; can be detected earlier than dipstick protein (includes albumin)
how is microalbuminuria measured?
by immunoassay on a 24 hour urine specimen
what levels of microalbuminuria are predictive of diabetic nephropathy?
50 to 200 mg/24 hr
In what condition, mainly, does albumin concentration increase?
dehydration
In what conditions does albumin concentration in the blood decrease?
malnutrition, liver disease, nephrotic syndrome (loss), chronic inflammation
what is the reference range for albumin?
3.5 to 5 g/dL
what protein is the largest fraction of plasma proteins? what are its functions?
albumin; mainly regulation of osmotic pressure, but also can carry some vitamins and hormones, fatty acids, bilirubin, ions, drugs…….
how is albumin measured in serum?
dye binding techniques using bromcresol green and bromcresol purple; these techniques allow albumin to be positively charged for binding the anionic dye; forming an albumin-dye complex and shifting the max absorbance of the dye. INCREASE IN ABSORBANCE is directly proportional to albumin concentration;
other methods include serum protein electrophoresis, and immunonephelometric or immunoturbidimetric methods
what is the reference range for total protein in serum?
6 to 8 g/dL
what conditions/diseases can cause an increase in total serum protein?
dehydration, chronic inflammation, and multiple myeloma
conditions causing decreased total protein in serum/plasma include:
nephrotic syndrome, malabsorption, hepatic insufficiency, malnutrition, overhydration, agammaglobulinemia
ref range for desirable total cholesterol, HDL, LDL, and Triglycerides:
<200mg/dL; HDL >60 mg /dL; LDL <100 mg/dL; trigs <150 mg/dL
MOst common test method for total cholesterol
enzymatic:
This assay is based on an enzyme-coupled reaction for determining free cholesterol and cholesterol esters. Esterified cholesterol is converted to cholesterol by cholesterol esterase. The resulting cholesterol is then acted upon by cholesterol oxidase to produce cholest-4-en-3-one and hydrogen peroxide and the corresponding ketone product. Hydrogen peroxide is then detected using sensitive and stable fluorescence probe.
https://www.sciencedirect.com/science/article/pii/S1021949818301467
HDL test methodologies, two major
- precipitate LDL and VLDL with dextran-sulfate-MgCl or heparin sulfate-manganese Cl, then assay supernatant w/ enzymatic technique
- HOMOGENOUS: use an antibody to bind LDL and VLDL, then use enzymatic technique which will only measure the HDL
Note that both use an enzymatic measurement method
How can LDL be measured? two ways
- directly: with homogenous assay that blocks HDL and VLDL from reacting with the dye in the enzymatic analysis
- calculation: Friedwald formula
LDL = TC - [HDL + triglyceride/5]
Method of measuring Trigs
enzymatic: uses lipase/glycerokinase/ glycerophosphate oxidase/peroxidase, you get a colored product.
list the main 5 risk factors for metabolic syndrome
decreased HDL, increased LDL, INcreased trigs, increased BP, increased blhood glucose
what is considered hypoglycemia in a nondiabetic adult, both mg/dL and mmol/L?
acc to BOC, < 55mg/dL or < 3.0 mmol/L
what is a normal CSF glucose range? what about whole blood vs serum?
CSF: 50 to 80 mg/dL (~2/3 the glucose reading)
whole blood glucose is lower than serum/plasma level; for example a whole blood may measure 75 and the serum 85 mg/dL
what is the approximate diff btw glucose in arterial vs venous ?
arterial and capillary are about 5 mg/dL higher
what would a normal fructosamine indicate in a T1DM pt even if the A1C and current BG is high?
their glucose control has improved over the past few weeks: fructosamine reflects average BG over past few weeks not months, so shows recent changes
how does HbgS affect A1C readings?
falsely elevates
what is the usefulness of copper reduction on infant stool?
to look for carbohydrate intolerance causing diarrhea, vs a virus or parasite;
increased reducing substances in stool can indicate a lack of enzymes needed to break down certain disaccharides or to malabsorption of monosaccharides
what are the products of glycolysis?
2 pyruvate, 4 ATP, 2 NADH
what are two commonly used enzymatic glucose testing methods?
one using hexokinase, and one with glucose oxidase
