Hormones and Receptors

Question 1

Hormone

Answer 1

chemical produced by certain cells, released into blood in minute amounts and has physiological effects on target cells at a distance

Question 2

endocrine gland

Answer 2

group of cells producing hormones

Question 3

3 classic categories of hormones

Answer 3

1. derivatives of tyrosine
   derivatives of 2. cholesterol (steroids)
2. peptides and proteins

Question 4

Tyrosine derivative hormones

Answer 4

epinephrine, norepinephrine, dopamine, thyroxine

Question 5

steroid hormones

Answer 5

testosterone, cortisol, estrogen, aldosterone, vit D, progesterone

Question 6

peptide hormones

Answer 6

oxytocin, vasopressin, angiotensin, thyrotropin releasing hormone, gonadotropin releasing hormone

Question 7

protein hormones

Answer 7

insulin, glucagon, growth hormone, ACTH, prolactin, thyroid stimulating hormone

Question 8

functional classificaitons of hormones

Answer 8

• regulation of water and mineral metabolism
• regulation of energy metabolism
• regulation of reproduction
• regulation of growth

Question 9

hormones involved in water and mineral metabolism regulation

Answer 9

vitamin D, aldosterone, vasopressin (ADH)

Question 10

hormones involved in energy metabolism

Answer 10

insulin, glucagon, cortisol

Question 11

hormones involved in reproductive regulation

Answer 11

estrogen, testosterone, progesterone

Question 12

hormones involved in growth regulation

Answer 12

growth hormone, testosterone, estrogen

Question 13

peptide and protein hormone synthesis

Answer 13

follow classical path for secreting proteins

• synthesized as pre-prohormones on ribosomes from mRNA
• targeted to RER where it is cleaved to prohormone – transported to Golgi for further processing/packaging into secretory vesicles
• endocrine organ secretes hormone via vesicular exocytosis in response to signals (Calcium dependent)

Question 14

How are most peptide/protein hormones transported in the blood

Answer 14

most are transported as free hormones, except GH, prolactin, and insulin-like growth factor

Question 15

half-life of protein/peptide hormones

Answer 15

limited due to proteases in blood

Question 16

precursor for all steroid hormones

Answer 16

cholesterol

Question 17

how are most steroid hormones transported in blood

Answer 17

carried by carrier proteins; equilibrium between free and bound forms

• only small fraction in free form (1-5%), but this is what is biologically active
• Bound form = reservoir

Question 18

half-life of steroid hormones

Answer 18

hours to days

Question 19

synthesis of steroid hormones

Answer 19

synthesized and released immediately into blood strea

Question 20

2 methods to measure hormone levels

Answer 20

bioassays (functional) and immunoassays (presence of hormone)

Question 21

bioassays

Answer 21

measure hormone activity using exogenous system (i.e. cell lines); can be complicated by fact that multiple hormones can have similar effects

Question 22

immunoassays

Answer 22

Radio-immunoassays (RIA) and enzyme linked immunosorbent assays (ELISA) measure Ab binding to specific region of hormone to measure hormone activity
- may not be useful if pt secreting abnormal form of hormone/don’t see function

• Radioimmunoassay–radiolabel hormone and add antibody. then add serum with nonlabeled hormone and see how much radiolabeled compound was displaced
• ELISA:
  Coat walls of thing with Ab to insulin, add serum sample so that insulin in serum binds Ab. Come in with 2nd Ab with enzyme attached that ill bind to insulin, measure enzyme activity to get amount of insulin

Question 23

where are receptors for peptide/protein hormones

Answer 23

on plasma membrane of target cells. Bind receptor–signalling cascade

Question 24

where are receptors for steroid hormones

Answer 24

nucleus/cytoplasm; affect gene expression

Question 25

how are hormones regulated

Answer 25

mainly by feeback loops

Question 26

2 classes of feedback loops

Answer 26

• hormone level regulated

- plasma concentration of metabolite or mineral is regulated

Question 27

positive feedback loops

Answer 27

rare in biology due to potential for causing instability in a process; example of positive feedback is oxytocin secretion during birthing process

Question 28

hormone secretion pattern

Answer 28

• often pulsatile; Also many regulated by diurnal variation and show characteristic circadian rhythms

Question 29

types of receptors that protein/peptide hormones use

Answer 29

1. G protein coupled hormones (Gs, Gi, Gq)
2. cytokine family(GH, prolactin)
3. EGF family

Question 30

Gs

Answer 30

when activated, alpha subunit activates adenylate cyclase causing increased cAMP

Question 31

Gi

Answer 31

decreases adenylate cyclase and thus cAMP

Question 32

Gq

Answer 32

activates phospholipase C that breaks down phosphoinositol in membrane to produce IP3 and DAG that cause downstream effects

Question 33

cytokine family

Answer 33

receptors, when bound, activate tyrosine kinase “Janus kinase” that phosphorylate on tyrosines downstream second messengers (aka signal transducers and activators of transcription- STATs; JAK/STAT pathway)

Question 34

EGF Family of receptors

Answer 34

receptor itself contains tyrosine kinase itself; when something binds, it dimerizes receptor and activates tyrosine kinase, activating signal transduction downstream

Question 35

enzyme converting cholesterol to pregenolone

Answer 35

desmolase

Question 36

drug inhibiting desmolase

Answer 36

ketoconazole

Question 37

acidophilic cells in AP

Answer 37

somatotrophs and lactotrophs

Question 38

basophilic cells in AP

Answer 38

gonadotrophs corticotrophs, thyrotrophs

Question 39

treat SIADH

Answer 39

demethaclocycline

Question 40

treat GH excess

Answer 40

• octreotide (somatostatin analog)
• DA agonist (i.e. bromocriptine)
• GH receptor antagonist (pegvisomant)