CH 1 General Principles

Question 1

How is endocrine function controlled?

Answer 1

hormones derived from circulation OR hormones produced locally OR neuroendocrine stimulation

Question 2

Where do Thyroid Hormones bind to its receptor?

Answer 2

Receptors are located within the cell. TH is special because it is an amino acid derivative that doesn’t bind on the cell surface. Instead, it is transported into the cell to bind to its receptor.

Question 3

How are protein/peptide hormones synthesized & released?

Answer 3

synthesis (ribosome) –> post-translation modification (ER) –> packaging + more modification (Golgi) –> complete hormone & “pro” fragments remain within a secretory vesicle until Ca++ induces hormone release

Question 4

What are steroid hormones derived from?

Answer 4

cholesterol

Question 5

Where are steroid hormones synthesized?

Answer 5

Adrenal Cortex, Gonads, Placenta

Question 6

What are AA hormones derived from?

Answer 6

Tyrosine

Question 7

Define endocrine effect.

Answer 7

hormone is released into the circulation & travels in blood

Question 8

Define paracrine effect.

Answer 8

hormone released from one cell that produces a biologic effect on a neighboring cell

Question 9

Define autocrine effect.

Answer 9

hormone produces a biologic effect within the same cell that released it

Question 10

What are the purposes of having a hormone bound to a binding protein?

Answer 10

serves as a reservoir for the hormone; prolong hormone’s half life; regulate the activity of hormone (by determining how much hormone is free)

Question 11

Define dynamic equilibrium between a hormone & its carrier protein

Answer 11

Dynamic equilibrium allows adjustments that prevent clinical manifestations of hormone deficiency or excess. Secretion of the hormone is adjusted rapidly following changes in levels of carrier proteins. For example, if more hormone is bound, more will be secreted to prevent hormone deficiency.

Question 12

How are hormones inactivated in the liver? & what are their possible fates?

Answer 12

phase I (proteolysis, oxidation, reduction, hydroxylation, decarboxylation) & phase II (methylation, glucoronidation, sulfation, or reduction with glutathione). Degraded hormones are then excreted by the liver (bile) or kidney (urine)

Question 13

How is affinity of a hormone determined?

Answer 13

by rate of dissociation & association for the hormone-receptor complex (under equilibrium conditions); a reflection of how tight a hormone-receptor interaction is

Question 14

define Kd

Answer 14

dissociation constant – hormone concentration required for binding 50% of receptor sites

Question 15

Define specificity of a hormone

Answer 15

the ability of a hormone receptor to discriminate among hormones with related structures

Question 16

What are the subunits of a G-protein coupled receptor? What variations are possible?

Answer 16

alpha, beta, gamma; can have alpha(s) / alpha(i) / alpha(q)

Question 17

Track the signal of a hormone that activates Protein Kinase A

Answer 17

hormone binds to Gprotein –> alpha(s) releases GDP & binds GTP –> Gprotein dissociates –> alpha(s) dissociates from beta/gamma –> alpha(s) activates Adenylate Cyclase to make cAMP –> cAMP activates PKA resulting in a cascade

Question 18

Track the signal of a hormone that activates Protein Kinase C

Answer 18

hormone binds to Gprotein –> alpha(q) releases GDP & binds GTP –> Gprotein dissociates –> alpha(q) dissociates from beta/gamma –> alpha(q) activates phospholipase C –> phospholipase C hydrolyzes phosphatidylinositol bisphosphate into diacylglycerol (DAG) & inositol triphosphate (IP3). –> DAG activates PKC resulting in a cascade. IP3 opens calcium channels.

Question 19

what specific enzyme terminates cAMP cascade?

Answer 19

phosphodiesterase

Question 20

what classification of enzyme stops a Gprotein cascade?

Answer 20

phosphatase

Question 21

Track the signal of a hormone that causes a Calcium cascade

Answer 21

hormone binds to Gprotein –> alpha(q) releases GDP & binds GTP –> Gprotein dissociates –> alpha(q) dissociates from beta/gamma –> alpha(q) activates phospholipase C –> phospholipase C hydrolyzes phosphatidylinositol bisphosphate into diacylglyceral (DAG) and inositol triphosphase (IP3). –> IP3 binds to Ca++ channels that release Ca++ –> high [Ca++] binds to calmodulin resulting in a cascade

Question 22

How do Receptor Protein Tyrosine Kinases work?

Answer 22

hormone binds –> activated receptor results in intrinsic enzymatic kinase activity that phosphorylates tyrosine residues on the catalytic domain of the receptor itself, increasing its kinase activity by creating a specific binding/docking site for additional proteins –> proteins are recruited and activated, initializing a downstream signaling cascade

Question 23

How does the Thyroid Hormone Receptor work?

Answer 23

Thyroid hormone must be transported into cell. The unoccupied receptor is BOUND to DNA & REPRESSES transcription. Binding of hormone allows transcription to take place.

Question 24

How does the Steroid Hormone Receptor work?

Answer 24

Steroid hormone receptor is initially bound to inhibiting receptor-associated proteins, unbound to DNA, and inactive. Binding of a steroid hormone causes the receptor to dissociate from inhibiting associated proteins. Hormone-Receptor complex translocates to nucleus to bind to DNA and initiate gene transcription.

Question 25

What are some methods of hormone receptor regulation for desensitization?

Answer 25

1) endocytosis & degradation via lysosome induced by hormone binding to cell surface receptor. 2) receptor phosphorylation. 3) change of a protein involved in signal transduction. 4) production of an inhibitor. 5) one hormone can downregulate/decrease expression of receptors for another hormone

Question 26

list the 3 ways hormone release is controlled.

Answer 26

neural, hormonal, nutrient/ion

Question 27

which endocrine organs are under neural control?

Answer 27

pancreas, adrenal gland

Question 28

Define Tropic Hormone.

Answer 28

A tropic hormone is one released from one endocrine organ that stimulates hormone release from another endocrine organ

Question 29

what are the three types of feedback mechanisms?

Answer 29

long loop, short loop, & ultra-short loop

Question 30

What is the difference between a decreased hormone response vs a decrease in hormone sensitivity?

Answer 30

When there is a decrease in responsiveness, no matter how high the hormone concentration, maximal response isn’t achieved. Decreased hormone sensitivity requires higher hormone concentrations to produces 50% of maximal response.