Fa: Endocrine - Embryology, Anatomy, & Physiology -2

Front 1

What part of TSH, LH, FSH, and hCG is the same? Which part determines its hormonal specificity?

Back 1

- α subunit is the same
- β subunit gives specificity

Front 2

What are the types of pancreatic cells with endocrine function?

Back 2

Islets of Langerhans:
- α cells
- β cells
- δ cells

Front 3

What is the source of Islets of Langerhans in the pancreas?

Back 3

Arise from pancreatic buds

Front 4

What is the function of the α, β, and δ cells in the Islets of Langerhans in the pancreas? Relative locations in Islet?

Back 4

- α cells: glucagon (peripheral)
- β cells: insulin (central) = Insulin is Inside
- δ cells: somatostatin (interspersed)

Front 5

How is insulin synthesized? Where?

Back 5

Takes place in β cells in Islets of Langerhans:
- Preproinsulin is synthesized in RER
- Cleavage of "presignal" generates Proinsulin
- Proinsulin is stored in secretory granules
- Cleavage of Proinsulin → exocytosis of Insulin and C-peptide

Front 6

If you see both elevated Insulin and C-peptide vs only elevated Insulin, how does this help your differential?

Back 6

- Elevated Insulin and C-peptide: Insulinoma
- Elevated Insulin without C-peptide: Exogenous Insulin administration

Front 7

How does insulin mediate its effects?

Back 7

1. Binds insulin receptors (tyrosine kinase activity)
2. Induces glucose uptake (carrier-mediated transport) in insulin dependent tissues
- Also induces gene transcription

Front 8

What happens when insulin binds to its receptor?

Back 8

- Tyrosine phosphorylation
- Phosphoinositide-3 kinase pathway
- Induces glycogen, lipid, and protein synthesis
- Vesicles containing GLUT-4 are placed in membrane to allow entry of glucose into cell

INsulin moves glucose INto cells

Front 9

What are the anabolic effects of insulin?

Back 9

- ↑ Glucose transport in skeletal muscle and adipose tissue
- ↑ Glycogen synthesis and storage
- ↑ Triglyceride synthesis
- ↑ Na+ retention (kidneys)
- ↑ Protein synthesis (muscles, proteins)
- ↑ Cellular uptake of K+ and amino acids
- ↓ Glucagon release

Front 10

What are the insulin-dependent glucose transporters? Locations?

Back 10

GLUT-4: adipose tissue and skeletal muscle

Front 11

What are the insulin-independent glucose transporters? Locations?

Back 11

- GLUT-1: RBCs, brain, cornea
- GLUT-5 (fructose): spermatocytes, GI tract
- GLUT-2 (bidirectional): β islet cells, liver, kidney, small intestine

Front 12

What type of glucose transporters are in the adipose tissue? Characteristics?

Back 12

GLUT-4: insulin-dependent glucose transporter

Front 13

What type of glucose transporters are in the skeletal muscle? Characteristics?

Back 13

GLUT-4: insulin-dependent glucose transporter

Front 14

What type of glucose transporters are in RBCs? Characteristics?

Back 14

GLUT-1: insulin-independent glucose transporter

Front 15

What type of glucose transporters are in the brain? Characteristics?

Back 15

GLUT-1: insulin-independent glucose transporter

Front 16

What type of glucose transporters are in the cornea? Characteristics?

Back 16

GLUT-1: insulin-independent glucose transporter

Front 17

What type of sugar transporters are in the spermatocytes? Characteristics?

Back 17

GLUT-5 (fructose): insulin-independent transporter

Front 18

What type of sugar transporters are in the GI tract? Characteristics?

Back 18

- GLUT-5 (fructose): insulin-independent transporter
- GLUT-2 (bidirectional): insulin-indepdent transporter - small intestine

Front 19

What type of sugar transporters are in the β islet cells? Characteristics?

Back 19

GLUT-2 (bidirectional): insulin-indepdent transporter

Front 20

What type of sugar transporters are in the liver? Characteristics?

Back 20

GLUT-2 (bidirectional): insulin-indepdent transporter

Front 21

What type of sugar transporters are in the kidneys? Characteristics?

Back 21

GLUT-2 (bidirectional): insulin-indepdent transporter

Front 22

What kind of fuel does the brain use?

Back 22

- Glucose for metabolism normally
- Ketone bodies during starvation

Front 23

What kind of fuel do RBCs use?

Back 23

Always utilize glucose because they lack mitochondria fro aerobic metabolism

Front 24

How do you remember the sites of insulin-indepdent glucose uptake?

Back 24

BRICK L:
- Brain
- RBCs
- Intestine
- Cornea
- Kidneys
- Liver

Front 25

What regulates insulin release?

Back 25

- Glucose
- GH
- β2-agonists

Front 26

How does glucose enter pancreatic β cells? What are the effects?

Back 26

3. Glucose enters β cells via GLUT-2 (bidirectional) channels
4. ↑ ATP generated from glucose metabolism
5. Closes K+ channels
6. Depolarizes β cell membrane
7. Opens voltage-gated Ca2+ channels, resulting in Ca2+ influx
8. Stimulates insulin exocytosis

Front 27

What is the source of glucagon? Function?

Back 27

- Made by α cells of pancreas

Functions in catabolism:
- Glycogenolysis and gluconeogenesis → make more glucose
- Lipolysis and ketone production → make alternative sources of energy

Front 28

What stimulates and inhibits glucagon secretion?

Back 28

- Secreted in response to hypoglycemia
- Inhibited by insulin, hyperglycemia, and somatostatin

Front 29

What is the function of CRH?

Back 29

↑ ACTH, MSH, and β-endorphin

Front 30

What causes ↓ CRH?

Back 30

Chronic exogenous steroid use

Front 31

What is the function of Dopamine on the pituitary?

Back 31

↓ Prolactin

Front 32

What is the effect of Dopamine Antagonists (eg, anti-psychotics) on the pituitary?

Back 32

Can cause galactorrhea (↑ prolactin)

Front 33

What is the function of GnRH?

Back 33

- ↑ FSH and LH
- Tonic GnRH suppresses the HPA axis
- Pulsatile GnRH leads to puberty and fertility

Front 34

What regulates GnRH?

Back 34

Regulated by Prolactin

Front 35

What is the effect of tonic GnRH release?

Back 35

Suppresses HPA axis

Front 36

What is the effect of pulsatile GnRH release?

Back 36

Leads to puberty and fertility

Front 37

What is the function of Prolactin?

Back 37

↓ GnRH

Front 38

What are the consequences of a pituitary prolactinoma?

Back 38

Amenorrhea (↓ GnRH) and Osteoporosis

Front 39

What is the function of Somatostatin on the pituitary?

Back 39

↓ GH and TSH

Front 40

How can you treat acromegaly?

Back 40

Somatostatin analogs (↓ GH)

Front 41

What is the function of TRH?

Back 41

↑ TSH and Prolactin

Front 42

What are the effects of Prolactin?

Back 42

- Stimulates milk production in breasts
- Inhibits ovulation in females and spermatogenesis in males by inhibiting GnRH synthesis and release
- Excessive prolactin associated with ↓ libido

Front 43

How is Prolactin regulated?

Back 43

- Tonically inhibited by Dopamine from hypothalamus
- Prolactin inhibits its own secretion by ↑ Dopamine synthesis and secretion
- TRH ↑ Prolactin secretion

Front 44

What drugs can be used to treat excess prolactin (such as prolactinoma)?

Back 44

Dopamine Agonists - eg, Bromocriptine
- Dopamine inhibits Prolactin secretion

Front 45

What drugs may stimulate prolactin secretion?

Back 45

- Dopamine antagonists (eg, anti-psychotics)
- Estrogens (OCPs, pregnancy)

Front 46

What are the effects of Growth Hormone (Somatotropin)?

Back 46

- Stimulates linear growth and muscle mass through IGF-1 / somatomedin secretion
- ↑ Insulin resistance (diabetogenic)

Front 47

What is the effect of GH on insulin?

Back 47

GH increases insulin resistance (diabetogenic)

Front 48

What regulates Growth Hormone release?

Back 48

- Released in pulses in response to GHRH (GH releasing hormone)
- Increases during sleep and exercise
- Inhibited by glucose and somatostatin

Front 49

What can excess secretion of GH be due to? What can it cause?

Back 49

- Could be due to pituitary adenoma
- Causes acromegaly (adults) or gigantism (children)

Front 50

What is the source of Anti-Diuretic Hormone (ADH)?

Back 50

- Synthesized in hypothalamus (supraoptic nuclei)
- Released by posterior pituitary

Front 51

What is the function of Anti-Diuretic Hormone (ADH)?

Back 51

- Regulates serum osmolarity (V2 receptors) and blood pressure (V1 receptors)
- ↓ serum osmolarity and ↑ urine osmolarity via regulation of aquaporin channel transcription in principal cells of renal collecting duct

Front 52

What diseases affect the levels / response to ADH?

Back 52

- 1° Polydipsia: ADH is suppressed
- Central Diabetes Insipidus (DI): ADH ↓
- Nephrogenic Diabetes Insipidus (DI): ADH ↑ (kidney is resistant to its effects)

Front 53

What can cause nephrogenic diabetes insipidus?

Back 53

Resistance to ADH can be mediated by a mutation in the V2 receptor (regulates serum osmolarity)

Front 54

How do you treat central diabetes insipidus?

Back 54

Desmopressin (ADH analog) - central DI is caused by insufficient production of ADH

Front 55

What are the types of receptors that ADH acts on? Effects?

Back 55

- V2 receptor: regulates serum osmolarity
- V1 receptor: regulates blood pressure

Front 56

How is ADH regulated?

Back 56

- Osmoreceptors in hypothalamus (1°)
- Hypovolemia (2°)