Glucose Regulation, relevant hormones, and Diabetes

Question 1

What hormones are primarily responsible for decreasing blood glucose and for increasing it?

Answer 1

insulin and glucagon

Question 2

What processes does glucagon stimulate and inhibit?

Answer 2

stimulates glycogenolysis and gluconeogenesis; inhibits glycolysis

Question 3

name 3 secondary hormones that deliberately cause an increase in blood glucose levels; which two are insulin antagonists?

Answer 3

cortisol, epinephrine, and growth hormone. cortisol and growth hormone are insulin antagonists.

Question 4

what does cortisol do?

Answer 4

regulates carb, fat & protein metabolism; water and electrolyte balance; suppresses inflammation ad allergic reactions

Question 5

In what disease is cortisol elevated and has lost diurnal variation (meaning higher in morning)?

Answer 5

Cushing’s syndrome

Question 6

differentiate between Cushing’s syndrome and Cushing’s Disease:

Answer 6

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

Question 7

What hormone regulates the release of cortisol? Where is cortisol and this stimulating hormone made?

Answer 7

ACTH: adrenal cortex (outer layer) and anterior pituitary

Question 8

Describe in simple terms the pathway from gland to gland in production of cortisol

Answer 8

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

Question 9

What are the 4 major adrenal hormones? which are made in the cortex and which in the medulla?

Answer 9

aldosterone, cortisol, and epinephrine and norepinephrine; The first two in the cortex, the latter two in the medulla

Question 10

what are the catecholamines, their purpose, and their metabolites? Test specimens for each?

Answer 10

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

Question 11

what does aldosterone do and where is it made?

Answer 11

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

Question 12

describe in simple terms the renin-angiotensin-aldosterone-system

Answer 12

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

Question 13

List 10 things increases in uncontrolled Diabetes mellitus

Answer 13

Blood glucose, urine glucose, urine specific gravity, Osmolality of blood and urine, glycohemoglobin (A1C!!), and ketones;

Anion gap, BUN, , cholesterol, and trigs

Question 14

what lab values are decreased in uncontrolled diabetes mellitus?

Answer 14

bicarbonate, and pH (more acidic)

Question 15

what is considered positive for diabetes mellitus in a random plasma glucose reading?

Answer 15

> 200 mg/dL

Question 16

what is considered diagnostic of diabetes mellitus with regards to fasting plasma glucose?

Answer 16

8 hours minimum fast; on greater than 2 occasions BG > 126 mg/dL

Question 17

what is considered diagnostic of DM in regards to a 2-hour plasma glucose test given a 75 gram glucose load?

Answer 17

same as a random, > 200 mg/dL

Question 18

WHat is the oral glucose tolerance test used to diagnose and what are the parameters of diagnosis?

Answer 18

gestational diabetes, done at 24 to 28 weeks; fasting, if > 92mg/dL ; 1 hour, > 180 ; 2-hr _>_153

Question 19

what is the cutoff for A1C for diabetes diagnosis?

Answer 19

> 6.5%

Question 20

what is the average reference range for normal fasting blood glucose?

Answer 20

70 to 99 mg/dL

Question 21

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?

Answer 21

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

Question 22

common methods of analyzing blood glucose:

Answer 22

enzymatic using either glucose oxidase or hexokinase

Question 23

what is the main form of lipid storage and what common methods are used to measure?

Answer 23

Triglycerides; enzymatic methods using lipase on fasting specimens

Question 24

WHat can be measured in the urine of diabetics to help predict nephropathy? Why not just test albumin?

Answer 24

microalbumin; can be detected earlier than dipstick protein (includes albumin)

Question 25

how is microalbuminuria measured?

Answer 25

by immunoassay on a 24 hour urine specimen

Question 26

what levels of microalbuminuria are predictive of diabetic nephropathy?

Answer 26

50 to 200 mg/24 hr

Question 27

In what condition, mainly, does albumin concentration increase?

Answer 27

dehydration

Question 28

In what conditions does albumin concentration in the blood decrease?

Answer 28

malnutrition, liver disease, nephrotic syndrome (loss), chronic inflammation

Question 29

what is the reference range for albumin?

Answer 29

3.5 to 5 g/dL

Question 30

what protein is the largest fraction of plasma proteins? what are its functions?

Answer 30

albumin; mainly regulation of osmotic pressure, but also can carry some vitamins and hormones, fatty acids, bilirubin, ions, drugs…….

Question 31

how is albumin measured in serum?

Answer 31

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

Question 32

what is the reference range for total protein in serum?

Answer 32

6 to 8 g/dL

Question 33

what conditions/diseases can cause an increase in total serum protein?

Answer 33

dehydration, chronic inflammation, and multiple myeloma

Question 34

conditions causing decreased total protein in serum/plasma include:

Answer 34

nephrotic syndrome, malabsorption, hepatic insufficiency, malnutrition, overhydration, agammaglobulinemia

Question 35

ref range for desirable total cholesterol, HDL, LDL, and Triglycerides:

Answer 35

<200mg/dL; HDL >60 mg /dL; LDL <100 mg/dL; trigs <150 mg/dL

Question 36

MOst common test method for total cholesterol

Answer 36

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

Question 37

HDL test methodologies, two major

Answer 37

1. precipitate LDL and VLDL with dextran-sulfate-MgCl or heparin sulfate-manganese Cl, then assay supernatant w/ enzymatic technique
2. 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

Question 38

How can LDL be measured? two ways

Answer 38

1. directly: with homogenous assay that blocks HDL and VLDL from reacting with the dye in the enzymatic analysis
2. calculation: Friedwald formula

LDL = TC - [HDL + triglyceride/5]

Question 39

Method of measuring Trigs

Answer 39

enzymatic: uses lipase/glycerokinase/ glycerophosphate oxidase/peroxidase, you get a colored product.

Question 40

list the main 5 risk factors for metabolic syndrome

Answer 40

decreased HDL, increased LDL, INcreased trigs, increased BP, increased blhood glucose

Question 41

what is considered hypoglycemia in a nondiabetic adult, both mg/dL and mmol/L?

Answer 41

acc to BOC, < 55mg/dL or < 3.0 mmol/L

Question 42

what is a normal CSF glucose range? what about whole blood vs serum?

Answer 42

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

Question 43

what is the approximate diff btw glucose in arterial vs venous ?

Answer 43

arterial and capillary are about 5 mg/dL higher

Question 44

what would a normal fructosamine indicate in a T1DM pt even if the A1C and current BG is high?

Answer 44

their glucose control has improved over the past few weeks: fructosamine reflects average BG over past few weeks not months, so shows recent changes

Question 45

how does HbgS affect A1C readings?

Answer 45

falsely elevates

Question 46

what is the usefulness of copper reduction on infant stool?

Answer 46

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

Question 47

what are the products of glycolysis?

Answer 47

2 pyruvate, 4 ATP, 2 NADH

Question 48

what are two commonly used enzymatic glucose testing methods?

Answer 48

one using hexokinase, and one with glucose oxidase