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USMLE Endocrine > Endocrine physiology > Flashcards

Endocrine physiology Flashcards

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USMLE® Step 1 flashcards
1
Q

What are examples of hormones which are produced by anterior pituitary basophils?

A

Be FLAT

  • FSH
  • LH
  • ACTH
  • TSH
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2
Q

What colour are the basophils?

A

Deep blue/purple

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3
Q

What are examples the hormones secreted by acidophils?

A

Acid PiG

  • Prolactin
  • GH
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4
Q

What colour are the acidophils?

A

Pink

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5
Q

What is the alpha subunit common to?

A
  • TSH
  • LH
  • FSH
  • hCG
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6
Q

Describe generally how the adrenal gland looks on histology?

A

Cortex is generally purple and the medulla is blue

  • Zona glomerulosa (thin)
  • Zona fasiculata (paler and thicker)
  • Zona reticularis (thin)
  • Adrenal medulla (blue)
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7
Q

What is the primary hormone produced by the zona reticularis?

A

DHEA

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8
Q

What are the carrier proteins called that transport ADH and oxytocin from hypothalamus to anterior pituitary?

A

Neurophysins

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9
Q

WHat is the precursor molecule that ACTH and MSH share?

A

Proopiomelanocortin

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10
Q

How can Cushing’s cause hyperpigentation?

A

Through proopriomelanocortin which is the precursor molecule to both MSH and ACTH

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11
Q

What is ADH release primarily triggered by?

A

Decreased plasma osmolarity

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12
Q

What does CRH release?

A
  • ACTH
  • MSH
  • B-endorphin
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13
Q

What is the GHRH analog which can be used to treat HIV-associated lipodystrophy?

A

Tesamorelin

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14
Q

What hormones can dopamine suppress?

A
  • Prolactin

- TSH

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15
Q

What ant pituitary hormones does somatostatin suppress?

A
  • GH

- TSH

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16
Q

How does natural contraception during breastfeeding happen?

A

Causes production of prolactin

  • Prolactin then suppresses the release of:
  • GnRH (thus LH and FSH)
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17
Q

What does primary prolactinoma cause?

A
  • Galactorrhea
  • Hypogonadism
  • Amenorrhea
  • Osteoperosis
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18
Q

What can GH also be called?

A

Somatotropin

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19
Q

What is an example of a somatostatin analog which can be used to treat acromegaly?

A

Octreotide

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20
Q

What does ADH cause when they act on V1 receptors?

A

Increase BP

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21
Q

What does ADH cause when they act on V2 receptors?

A

Decreased serum osmolarity (increase urine)

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22
Q

What cells does ADH act on in the renal collecting ducts?

A

Principle cells of the collecting duct (causes increase in Aquaporin insertion)

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23
Q

What is Leuprolide?

A

GnRH agonist

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24
Q

TRH causes the release of TSH and can trigger the secretion of what other hormone?

A

Prolactin

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25
Q

Via what pathway does dopamine inhibit prolacin secretion?

A

Tuberoinfundibular pathway of hypothalamus

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26
Q

What is an example of a dopamine agonist which can be used in the treatment of prolactinoma?

A

Bromocriptine

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27
Q

What are examples of dopamine antagonists which can cause prolactin secretion?

A
  • Antipsychotics
  • Metoclopramide
  • Estrogen
28
Q

What are the 3 forms plasma Ca2+ may exist?

A
  • Ionised free ~ 45%
  • Albumin ~ 40%
  • Anions ~ 15%
29
Q

How does Mg2+ affect PTH levels?

A

A decrease in Mg2+ causes increased PTH and a large decrease causes a decrease in PTH

30
Q

How does pH affect calcium and PTH levels?

A

Increased pH promotes increased protein binding, which decreases free calcium levels and therefore increase PTH levels

31
Q

What is synthesised in the rough endoplasmic reticulum of the Beta cells?

A

Preproinsulin

32
Q

What forms is insulin stored in before being exocytosed?

A
  • Preproinsulin is synthesised in the RER of the B cells
  • Cleaved to produce proinsulin
  • Proinsulin is stored in secretory granules
  • Proinsulin is exocytosed into insulin and C-peptide
33
Q

What structure is in natural insulin but not in synthetic?

A

C-peptide

34
Q

What bonds are present in insulin?

A

2 disulfide bonds

35
Q

Where can GLUT1 transporters be found?

A
  • RBCs
  • Brain
  • Cornea
  • Placenta
36
Q

Where can GLUT2 transporters (bidirectional) be found?

A
  • Beta islet cells
  • Kidneys
  • Liver
  • GI tract
37
Q

Where can GLUT3 transporters be found?

A
  • Brain

- Placenta

38
Q

Where can GLUT5 (fructose) transporters be found?

A
  • Spermatocytes

- GI tract

39
Q

Where can SGLT1/2 transporters be found?

A
  • Kidney

- Small intestine

40
Q

Where can insulin independant glucose uptake occur?

A

BRICK LIPS

  • Brain
  • RBCs
  • Intestine
  • Cornea
  • Kidneys
  • Liver
  • Islet B cells
  • Placenta
  • Spermatocytes
41
Q

Where is the satiety centre located that leptin acts on?

A

Ventromedial area of hypothalamus

42
Q

Why is there a bigger insulin response with oral glucose compared with IV?

A

Incretins:
- glucagon-like peptide (GLP-1)
- Glucose-dependent insulinotropic polypeptide (GIP)
These are released after meals and increase Beta cell sensitivity to glucose

43
Q

Where are the Beta cells located in the islets?

A

Centrally

44
Q

How does Insulin release happen in the Beta cells?

A
  • Glucose enters the cell via GLUT2
  • Glycolysis causes increased ATP/ADP ratio
  • ATP closes ATP sensitice K+ channel
  • Depolarisation occurs voltage-gated Ca2+ channels open
  • Increased intracellular Ca2+
  • Insulin exocytosed from the granules
45
Q

How does epinephrine effect insulin release?

A

Insulin release inhibited and plasma glucose increased

46
Q

What receptors does insulin act on in the pancreas?

A
  • B2 receptors (which increase insulin release)
  • a2 receptors (decrease insulin release)
  • Alpha effect is dominant effect in pancreas therefore plasma glucose increased
47
Q

What enzyme is induced by insulin?

A

Glucokinase (it converts glucose into G6P)

48
Q

Why is a bidirection glucose transporter (GLUT2) needed in kidney or liver cells?

A

Gluconeogenesis

49
Q

What is the insulin receptor made out of?

A
  • 2 a units (extracellular)
  • 2 B units (transmembrane)
    Connected by disulfide bonds
50
Q

What enzyme does insulin activate by activating the insulin receptor?

A

Tyrosine kinase

51
Q

What can the brain not use for energy?

A

fatty acids

- Uses glucose/ketones

52
Q

Why do RBCs use GLUT1 for glucose uptake?

A

They lack mitochondria therefore depend on glycolysis

53
Q

What is lipase inhibited by?

A

Insulin

54
Q

Describe how insulin causes glucose uptake into cells?

A
  • Phosphorylates tyrosine on the tyrosine kinase (insulin) receptor
  • Recetpror binds substrates (insulin recepetor substrates) (IRS-1,2) these mediate downstream effects
  • PIK3 pathway and RAS/MAP kinase pathway
  • Phosphatidylinositol 3-kinase pathway forms PIP3 from PIP2
  • Glycogen, lipid synthesis + GLUT4 releaase from vesicles
  • RAS/MAP kinase pathway causes cell growth and DNA synthesis
55
Q

What pathway is responsible for the uptake of GLUT4 and glycogen, lipid and protein synthesis?

A

Phospoinositide-3 kinase pathway

56
Q

What tissues are insulin dependent?

A

Muscle and fat

57
Q

How does insulin affect glycogen and glucose levels?

A
  • Glycogen synthesis (activates glycogen synthase and inhibits glycogen phosphorylase)
  • Inhibits gluconeogenesis (increases fructose-2,6-biphosphate levels and inhibits frictose 1,6 biphosphate 1)
58
Q

How does cortisol regualte itself?

A

Excess cortisol decreases CRH and ACTH and cortisol secretion

59
Q

What are the functions of cortisol?

A

A BIG FIB

  • Increases apetite
  • Increases BP (upregulates a1 receptors) and can bind to aldosterone receptors
  • Increases insulin resistance (diabetogenic)
  • Increases gluconeogenesis, lipolysis and proteolysis (decreased glucose utilisation)
  • Decreased Fibroblast activity
  • Decrease Inflammatory and immune responses (inhibits leukotrienes and prostaglandins, WBC adhesion, neutrophilia. Blocks histamine release from mast cells, eosinophilia, lymphopenia. Blocks IL-2 production
  • Decreases bone formation thru decreasing osteoblast activity
60
Q

What processes does glucagon promote?

A
  • Glycogenolysis
  • Gluconeogenesis
  • Lipolysis
  • Ketogenesis
61
Q

What is glucagon inhibited by?

A
  • insulin
  • Amylin
  • Somatostatin
  • Hyperglycemia
62
Q

What genetic disorder causes increased ghrelin production?

A

Prader-Willi syndrome (deletion of chr15 from father)

63
Q

Where does ghrelin act on?

A

Lateral area of hypothalamus (hunger centre)

64
Q

Do obese people have increased leptin?

A

Yes (incr adipose) but they are resistant/tolerant to its anorexigenic effect

65
Q

How does sleep deprivation effect leptin?

A

Decreases leptin (more hungry/less satiated)

66
Q

What do endocannabinoids act on?

A

Cannabinoid receptors in hypothalamus and nucleus accumbens, 2 key brain areas for the homeostatic and hedonic control of food intake - increases apetite

USMLE Endocrine (8 decks)

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