Endocrine: 1. Komar : Biomedical Foundation Of The Endocrine System & Pathophysiology Of The Hypothalamus/pituitary

Front 1

What is desensitzation?

a few examples of how it occurs?

Back 1

same amount of hormone, but diminished response

can occur through:

Uncoupling of the G-protein (can be triggered by modification of the receptor)

endocytosis (ex: insulin receptor)

Modification by other proteins resulting in decreased signaling activity (without changing receptor #)

Altered expression level of receptors

One hormone may regulate expression, internalization, etc of the receptor for a different hormone

Front 2

in general, what are important regulators of tyrosine kinases?

Back 2

phosphatases

cleave phosphate and thus regulate the cascade

Front 3

what kind of receptors do thyroid and steroid hormones utilize?

Back 3

internal receptors that are transcription factors

Front 4

the pancreatic beta cell is an example of what type of feedback loop?

Back 4

feedback loop regulating ‘free standing’ endocrine organ

glucose activates pancreatic beta cell-->insulin release-->reduces glucose-->turns off pancreatic beta cell

Front 5

• Discuss the impact of half-life, protein binding, metabolism and excretion of thyroid hormones

Back 5

Bound to plasma proteins:
Thyroid hormone binding globulin
Transthyretin
Albumin

Long half lives (days, T4 longer than T3):

Peripheral metabolism through deiodination:
Metabolized to active or inactive forms

Front 6

Regulation of Anterior Pituitary Hormone Secretion? (axis for activation/regulation; general)

Back 6

Hypothalamus--->Pituitary-->Target Gland

Target gland then sends info back to pituitary and hypothalamus to shut off

Front 7

what is glycosylation with respect to peptide hormone synthesis?

Back 7

makes proteins more stable, less likely to be broken down

Front 8

intercrine

Back 8

gap junctions allow for hormonal communication btw 2 cells

Front 9

common first step in steroid hormone synthesis?

Back 9

cholesterol to pregnenolone

Front 10

autocrine

Back 10

cell releases hormone that effects self

Front 11

what step will prevent steroid synthesis?

Back 11

deficiency in StaR

required for transport into the mitochondria

Front 12

when assessing endocrine disease, which is assessed first (structure/function

Back 12

Function assessed 1st

Structure assessed 2nd

Front 13

Binding to receptor tyrosine kinases stimulates a cascade of

Back 13

phosphorylation events

that starts the whole cascade

Front 14

sources of cholesterol for steroid synthesis

Back 14

de novo

LDL/HDL

Front 15

what is dynamic assesment of endocrine function?

Back 15

stimulation: to confirm hypofunction

inhibition: to confirm hyperfunction

Front 16

key step in formation of Eicosanoids? enzyme responsible?

Back 16

release of arachidonic acid (done by Phospholipase A2 or Phospholipase C)

Front 17

paracrine

Back 17

one cell releases hormone that effects the neighboring cell

Front 18

intacrine

Back 18

cell takes up precursor of hormone, gets activated hormone, hits intracellular receptor

(example: androgens)

Front 19

solocrine

Back 19

cell releases hormone into lumen (such as in GI)

Front 20

describe Endocrine organ hypofunction

Back 20

Primary endocrine organ failure – genetic; acquired
agenesis
genetic defect in hormone biosynthetic pathway (CAH)
destruction (autoimmune; infection)
deficiency in precursor (iodine)


Production of abnormal hormone

Secondary organ failure (hypogonadal due to hypopituitarism)

Front 21

describe hemocrine hormonal communication (the main endocrine form of communication)

Back 21

chemical messenger produced by cell, secreted into blood stream, and has effect at a distance

Front 22

juxtacrine

Back 22

things on the cell membranes of 2 cells come into contact and effect one another

Front 23

Thyroid hormone is a derivative of what?

Back 23

tyrosine

Front 24

describe Endocrine organ hyperfunction (primary/secondary)

Back 24

Primary (tumor – parathyroid adenoma; autoimmune – Grave’s)

Secondary (ACTH pituitary adenoma; ectopic production - cancer)

Front 25

Steroid hormones are synthesized from ....? are they stored?

Back 25

Cholesterol

not stored

(peptides are made from cleavage of protein, and are stored)

Front 26

3 chemical classes of hormones?

Back 26

Peptide/polypeptide/protein
Insulin, growth hormone, calcitonin…..
Range from 3 AAs (TRH) to 198 AAs ( Prolactin)

Lipid derivatives
Steroid (cortisol, estradiol, aldosterone…..)
Eicosanoid (prostaglandins, thromboxanes…)

Amino acid derivatives
Epinephrine, norepinephrine, dopamine, T3, T4

Front 27

Several different methods can be used to measure hormone levels, what is the key one?

Back 27

Immunoassays

Front 28

Eicosanoids are synthesized from what?

Back 28

fatty acids

Front 29

• Discuss the impact of half-life, protein binding, metabolism and excretion of peptide hormones

Back 29

Short half lives:
Those that are glycosylated are more stable

Are not protein bound:
Exceptions include GH, vasopressin, oxytocin

Eliminated through multiple mechanisms:
Serum proteases
Receptor mediated endocytosis followed by lysosomal degradation
Kidney/liver excretion