Lecture 2+3

Question 1

3 classes of anterior pituitary hormones?

Answer 1

glycoproteins:
FSH, LH, and hCG (pregnancy)
alpha chains are identical, beta differ

POMC:
ACTH

lactogens:
GH, PRL, and hPL (pregnancy)

Question 2

growth hormone?
secreted by?
stimulators? inhibitors?

Answer 2

secreted by somatotrophs

inhibited by somatostatin

stimulated by hypoglycemia, ghrelin, and GHRH (major)

Question 3

mechanism of GHRH

Answer 3

binds to receptor
increase cAMP and Ca

thus increased GH synthesis and exocytosis

Question 4

mechanism of somatostatin on GH

Answer 4

decreased cAMP and decreased Ca

inhibits DNA transcription and GH exocytosis

Question 5

mechanism of GH on target cell

Answer 5

activate tyrosine kinase receptor

increase gene expression

Question 6

direct actions of GH on the liver, fat, and muscle

Answer 6

Liver:
increase blood glucose
increase IGF
increase IGF-BP

fat:
increase lipid breakdown
decreased glucose intake

muscle:
increase AA uptake
increased protein synthesis
decreased glucose intake

Question 7

blood glucose vs insulin

Answer 7

increased blood glucose leads to increased insulin

GH always increases blood glucose

insulin is needed for growth

Question 8

IGF1 or somatomedin C

role of IGF’s

Answer 8

produced mainly in the liver in response to growth hormone

role:
promote linear growth
increase organ size and function

low amounts of IGF will lead to dwarfism

Question 9

hypersecretion of GH

Answer 9

usually due to tumor in AP

the result can be giantism or acromegaly

giantism occurs before the closure of the epiphyseal plates

Question 10

how phenylalanine can produce dopamine, norepinephrine, and epinephrine?

Answer 10

phenylalanine is converted to tyrosine by phenylalanine hydroxylase (H4 is a cofactor)

tyrosine is converted to DOPA by tyrosine hydroxylase (H4 is a cofactor)

DOPA to dopamine is done by DOPA decarboxylase (PLP or B6 is the cofactor)

dopamine to norepinephrine by dopamine Beta hydroxylase (vitamin C is cofactor)

norepi to epinephrine by Phenylethanolamine N
methyl transferase (SAM is cofactor)

Question 11

Parkinson’s disease

Answer 11

neurodegenerative disorder due to loss of dopamine producing cells in the basal ganglia

characterized by movement disorders

Question 12

how to measure norepinephrine or epinephrine?

how are they broken down?

Answer 12

urinary VMA levels

both catecholamines are broken down by either MAO or COMT

vma =Vanillylmandelic acid

Question 13

what is the end product of dopamine degradation?

Answer 13

HVA by either MAO or COMT

HVA is homovanillic acid

Question 14

what may high urinary VMA point to?

Answer 14

pheochromocytoma

seen to have overproduction of epinephrine

symptoms:
headache, sweating, tachycardia, hypertension

Question 15

how is serotonin synthesized?
how is melatonin?
how is serotonin excreted?

Answer 15

tryptophan is converted to 5 hydroxy tryptophan by tryptophan hydroxylase (BH4 is cofactor)

5 hydroxy tryptophan is converted to serotonin by amino acid decarboxylase (B6 is cofactor)

serotonin is converted to 5-HIAA by MAO for excretion

melatonin is derived from serotonin

Question 16

Carcinoid syndrome?

Answer 16

tumor of the serotonin producing cells in the gut (APUD cells)

seen to have flushing, sweating, diarrhea, bronchospasm

increased 5-HIAA in urine

Question 17

reactions that need Tetrahydrobiopterin (BH4)?

Answer 17

1. phenylalanine hydroxylase (phe to tyr)
2. tyrosine hydroxylase (Tyr to DOPA)
3. tryptophan hydroxylase (Trp to 5-hydroxy trp)

Question 18

Tetrahydrobiopterin deficiency

Answer 18

decreased synthesis of neurotransmitters

results in severe mental impairment

Question 19

T3 and T4 hormones?

Answer 19

tyrosine residues (3 / 4) are Iodinated

T4, less active, is converted to T3, more active, by 5’ Deiodinase

Question 20

steps in formation of thyroid hormone?

Answer 20

trapping iodine in cell

iodinate the thyroglobin protein (post-translational)

coupling of the tyrosine side chains

release

Question 21

functions of TPO or thyroperoxidase?

Answer 21

1. TPO fixes iodine to thyroglobulin

2. then acts as a peroxidase (link the tyrosine chains)

Question 22

iodine deficiency

Answer 22

result in hypothyroidism and goiter due to increased TSH secretion

if occurring during fetal development congenital hypothyroidism can occur

Question 23

graves disease

Answer 23

a form of hyperthyroidism that occurs due to overproduction of thyroid hormone
(antibody that mimics TSH)