Clinical Chemistry Flashcards
Where is the thyroid gland and what is its function?
butterfly shape organ located in the neck, responsible for the secretion of thyroid hormones
Where is the parathyroid and what is it’s function?
4 yellowish organ located within the thyroid gland, primary responsibility in maintaining calcium levels
What is thyroglobulin?
main storage site of thyroid hormones and is the precursor to thyroid hormones
What is regulated by the thyroid hormones and secreted from the pituitary gland?
Thyrotropin (TSH)
What are the two major thyroid hormones?
T3 (thriiodothyronine) and T4 (thyroxine)
What is the function of T3?
regulates metabolism, growth and development
- 20% of T3 is derived from the thyroid gland
- most comes from de-iodinzation of T4 from liver, kidney and muscle
What is the function of T4?
major hormone secreted from the thyroid gland
-most is bound by TBG FT4, only the unbound fraction is biologically active
What are the additional biologically inactive forms of T4?
rT3, MIT and DIT
-MIT and DIT are precursors to T3 and T4
What is the function of calcitonin?
- not much is known about physiological role in humans
- release is stimulated by increasing circulating calcium levels in the blood
- serves as an antagonist to PTH-inhibits osteoclastic bone activity
How is thyroid hormone synthesized in the thyroid gland? (5 steps)
- Iodine is ingested in food and water, concentrated in thyroid gland
- Incorporated into the amino acid tyrosine (Thyroglobulin)
- Concentrated iodine is oxidized and bound to tyrosyl residues on thyroglobulin-catalyzed by thyroid peroxidase (TPO)
- MIT and DIT are formed as a result
- TSH stimulates lysosomes to cleave T3 and T4 and release into blood stream
TSH is released in a ____nature and is _____?
pulsating and diurnal
Who am I?
more loosely bound to carrier protein, more metabolically active, 99.7% bound to TBG and 0.3% free form
T3
Who am I?
70 times more in circulating in peripheral blood, strongly bound to carrier protein: 70-75% to TBG, 15-20% to TBPA and 10% albumin
T4
Common Lab tests
TSH, FT4 and FT3
Which factors serve as markers for thyroid tumors?
Thyroglobulin or Calcitonin
Can a goiter be present in both hyper and hypothyroidism?
yes
Causes for hypothyroidism
autoimmune, iodine deficiency and radioactive iodine treatment
primary dysfunction
thyroid is the site of defect
secondary dysfunction
pituitary is the site of defect
tertiary dysfunction
hypothalamus is site of defect
What is another word used for hyperthyroidism?
thyrotoxicosis
What disease am I?
autoimmune disorder, 80% of all hyperthyroidism
TSH decreased
FT4 increaseed
Graves disease
What am I?
FT4 decreased
TSH increased
hypothyrodism
Causes of hypothyroidism
radioactive treatments or ablation, low iodine intake, certain foods or meds
What is the treatment for hypothyroidism?
levothyroxine (synthetic thyroid hormone)
Hashimoto’s Thyroiditis
- autoimmune condition commonly associated with permanent hypothyroidism
- is a primary hypothyroidism resulting in insufficient T4 available to tissues
Graves disease
- autoimmune disorder characterized by diffuse, toxic hyperplasia
- caused by IgG antibody vs Thyroid TSH receptor=overproduction of thyroid hormones
Euthyroid Sick Syndrome
TSH or thyroid hormones may be abnormal but the thyroid gland is functioning normally, often stimulated hypothyroidism
-FT4 remains normal
definition of ischemia
local, temporary lack of blood supply due to obstruction
What is the most common cause of atherosclerosis?
acute coronary syndrome
What are the lab markers for an MI?
LDH (flip), troponin, CK, CKMB ratio, myoglobin, AST, homocysteine, hsCRP and CHF=BNP
CK
used as a general screen but not very specific, increase in 6 hours, back to normal in 3 days
CKMB
rise 4-6 hours
peak 12-24 hours
normal 2-3 days post onset
CKMB/CK index
<3 muscle and >6 MI
LD1/LD2 flip
LD1>LD2 peak at 48 hours, back to normal within ten days
Troponin (Gold Standard)
binds calcium and regulates muscle contraction rise: 4-6 hours peak: 12-18 hours normal: 4-10 days normal level: 0.1 ng/mL
Myoglobin
O2 binding heme protein found in cardiac and skeletal muscle
rise: 1-3 hours
peak: 6-9 hours
normal: 18-24 hours
CRP
acute phase protein produced by liver in response to infection, injury and inflammation, non specific marker for inflammation
hsCRP
- more cardiac specific, small changes can be seen earlier
- higher hsCRP associated with higher risk of future cardiac related morbidity and mortality
homocysteine
-amino acid found in the blood
hyperhomcyteniemia is related to increased risk of
CHD, stroke and peripheral vascular disease
What are natriuretic peptides?
hormones that play an important role in cardiac homeostasis
What are the natriuretic peptides that are markers for CHF?
ANP, BNP, CNP and DNP
Name the five enzymes that are used to assess liver function plus a sixth extra parameter
ALT, AST, ALKP, GGT and LDH
5 prime nucleotidase
Where is ALT found and how long does it stay elevated?
- found in hepatocytes (specific to liver)
- stays elevated longer than AST
Where is AST found and what do values greater than 400 mean?
- found in many sources (not as specific)
- values over 400 suggest acute viral hepatitis
ALT>AST
hepatitis, most liver disease
AST>ALT
cirrhosis
Where is ALKP found and what do elevated levels mean?
- found in many sources throughout the body
- highest amounts found in obstruction (can help differentiate from hepatocellular injury)
- mild elevation in cirrhosis or hepatitis
What is GGT and where is it found?
- membrane enzyme that helps amino acid cross cell membrane
- found in liver cells and bile duct walls
- sensitive marker for obstructive cholestasis and ETOH intoxication
What if ALKP is high and GGT is normal
probably not liver
Where is LDH found and when are levels elevated?
- widely distributed in body (high amount in RBC)
- not found in bone
- moderate elevation: hepatobiliary disease
- slight elevation: biliary tract disease
- high elevation: hepatic carcinoma
5’ Nucleiotidase
- widely distributed in cells
- no bone source
both______&______with be increased in liver disease but only _____will be elevated in bone disease
5’ nucleosidase and ALKP
ALKP
5 additional tests for liver function
ammonia, albumin, immunoglobulins, protime and AFP
Ammonia is normally converted to____ by the _____
urea by the liver
-reflects the liver’s ability to convert ammonia to urea
When will ammonia levels be increased?
liver failure, hepatic carcinoma or in Reye Syndrome
Methods to test ammonia
Caraway, Nessler’s and enzymatic reaction
Normal reference range for ammonia
20-50umol/L
>100 is critical
Where is albumin synthesized?
liver
IgG and IgM may both be elevated in…
chronic active hepatitis
IgM may be elevated in…
primary biliary cirrhosis
IgA may be elevated in…
alcoholic cirrhosis
If patient has liver damage the protime will be…
prolonged because clotting factors are synthesized in the liver
What is a common tumor maker of the liver?
AFP
Bu-unconjugated bilirubin (indirect)
bound to albumin, insoluble in water, NOT filtered and excreted by kidney
Bc-conjugated bilirubin (direct)
water soluble and can be filtered and excreted
Total bilirubin=
Bu+Bc
What is delta bilirubin?
conjugated bilirubin that is bound to albumin. Can occur when liver is conjugating effectively but it cannot be excreted from the liver. Only seen in significant obstruction
What is urobilinogen?
derived from bilirubin in GI tract, oxidized by intestinal bacteria to form urobilin, adds color to stool
Is urobilinogen present in obstruction?
no it is absent
When is urobilinogen increased?
hemolytic disease, defective liver cell function and hapatitis
What causes neonatal jaundice?
-an enzyme deficiency of glucoronyl transferase (one of the last enzymes to be activated in prenatal life)
What is kernicterus?
bilirubin deposited in nuclei of brain and nerve cells, is life threatening, may require exchange transfusion
What is ascites fluid?
presence of free fluid in the peritoneal cavity
commonly seen in: cirrhosis due to alcoholism, hepatitis and hepatic vein obstruction
Pre hepatic jaundice bilirubin values
Total: increased
Unconjugated: increased
Conjugated: normal
Pre hepatic jaundice what will be seen in the toilet?
- Bilirubin will NOT be seen in UA
- Urobilinogen is seen in urine as a result of increased bilirubin being conjugated
- Stool will be dark brown
Hepatic Jaundice bilirubin values
Total: increased
Unconjugated: variable
Conjugated: variable
Hepatic Jaundice can be one of two problems
biliary metabolism or transport
In biliary increase in unconjugated bilirubin
In transport increase in conjugated bilirubin
Disorders of unconjugated hyperbilirubinemia
Gilberts Disease, Criggler-Najjar, and Neonatal Jaundice
Disorders of conjugated hyperbilirubinemia
Dubin-Johnson syndrome and Rotor Syndrome
What is Gilbert’s Disease?
inherited disease, problem with encoding of enzyme that catalyzes bilirubin conjugation
What is Criggler Najjar?
inherited disease, similar to Gilbert’s but more severe
What is Dubin-Johnson disease?
rare inherited disorder causing a deficiency in a transport protein, problem is in transporting bilirubin out of the cells to be excreted in bile
What is Rotor Syndrome?
clinically similar to Dubin-Johnson, defect is not known, dark granules no seen on biopsy
Post hepatic jaundice bilirubin values
all elevated
What will you see in the toilet for post hepatic jaundice?
no urobilinogen in the urine, stool with no color
What are the methods for measuring bilirubin?
Ehrlich’s method, Van Den Bergh, Malloy and Evelyn and Jendrassik and Grof
Which bilirubin detection test measures total bilirubin and the Bu
Jendrassik and Grof
What is cholestasis?
stoppage of bile flow, commonly due to bile duct obstruction
Endocrine function of the pancreas
release hormones: alpha cells (glucagon) and beta cells (insulin), somatostatin and pancreatic polypeptide
Exocrine function of the pancreas
release AMY and Lipase
