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Duke-NUS MS1 > RA18 Endocrine > Flashcards

RA18 Endocrine Flashcards

1
Q

Endocrine

Phys 35 Endocrine System General Concepts

A

Hormome travels through the blood circulation to act on distant target cells

Distant-signalling

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2
Q

Paracrine

Phys 35 Endocrine System General Concepts

A

Hormone is secreted into the interstital fluid to act locally on nearby target cells

Nearby-signalling

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3
Q

Autocrine

Phys 35 Endocrine System General Concepts

A

Hormone is secreted into interstitial fluid to act on the cell that produced it

Self-signalling

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4
Q

How are hormones regulated? (3 ways)

Phys 35 Endocrine System General Concepts

A
  • Rate of hormone production (+ve/-ve feedback)
  • Rate of hormone delivery (perfusion, mass action law)
  • Rate of hormone excretion/degredation (half-life)
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5
Q

Peptide hormones
- Consists of/derived from?
- Synthesis
- Storage
- Solubility in plasma
- Carrier
- Receptors
- Response time
- Half life (effect time)
- Examples

Phys 35 Endocrine System General Concepts

A
  • Consists of 3 or more amino acids
  • Pre-prohormone in RER -> cleave signal sequence -> prohormone in Golgi aparratus -> packaged and trimmed -> active hormone in secretory vesicle
  • Stored in secretory vesicles
  • Soluble
  • Not bound to carrier
  • Bind cell surface receptors -> activate second messenger cascade
  • Fast acting
  • Short half life
  • E.g. glucagon, insulin
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6
Q

Steroid hormones
- Consists of/derived from?
- Synthesis
- Storage
- Solubility in plasma
- Carrier
- Receptors
- Response time
- Half life (effect time)
- Examples

Phys 35 Endocrine System General Concepts

A
  • Derived from cholesterol
  • Cholesterol -> pregnenolone (rate limiting step)
  • Synthesised on demand (by adrenal cortex, gonads, placenta), NOT stored
  • Insoluble
  • Bound to carrier
  • Bind intracellular receptors -> activate gene transcription
  • Slow acting
  • Long half life
  • E.g. estrogen, cortisol
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7
Q

Amino acid derivatives: thryoid hormones
- Consists of/derived from?
- Solubility in plasma
- Carrier
- Receptors
- Response time
- Half life (effect time)
- Examples

Phys 35 Endocrine System General Concepts

A
  • Derived from amino acids (tyrosine)
  • Insoluble
  • Bound to carrier
  • Bind intracellular receptors -> activate gene expression
  • Slow acting
  • Long half life
  • E.g. T3, T4
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8
Q

Amino acid derivatives: catecholamines
- Consists of/derived from?
- Solubility in plasma
- Carrier
- Receptors
- Response time
- Half life (effect time)
- Examples

Phys 35 Endocrine System General Concepts

A
  • Derived from amino acids (tyrosine)
  • Soluble
  • Not bound to carrier
  • Bind cell surface receptors -> activate second messenger pathway (signal cascade)
  • Fast acting
  • Short half life
  • E.g. epinephrine, norepinephrine
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9
Q

Where are carrier proteins synthesised?

Phys 35 Endocrine System General Concepts

A

Liver

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10
Q

Function of carrier proteins

Phys 35 Endocrine System General Concepts

A
  • Extend half life of hormones in circulation (protect hormones from degredation/excretion)
  • Sequester hormones from target cell receptor (i.e. hormones bound to carrier cannot bind to receptor; only free hormones are active)
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11
Q

Total hormone concentration in the blood

Phys 35 Endocrine System General Concepts

A

Bound (to carrier) + free

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12
Q

Plasma insoluble hormones bind to (…) receptors. Plasma soluble hormones bind to (…) receptors.

Phys 35 Endocrine System General Concepts

A

Plasma insoluble hormones bind to intracellular receptors. Plasma soluble hormones bind to cell surface receptors.

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13
Q

Adaptation/desensitisation of receptors

Phys 35 Endocrine System General Concepts

A

Chronically elevated level of hormone -> diminished cell response

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14
Q

Rebound of receptors

Phys 35 Endocrine System General Concepts

A

Prolonged absence of hormone -> increased receptor numbers -> hyperactive with return of hormone

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15
Q

Inactivation of hormonal response (3 ways)

Phys 35 Endocrine System General Concepts

A
  • Removal of hormone from circulation
  • Down regulation of hormone (sequestration i.e. endocytosis of receptor, uncoupling of receptor from donwstream signalling)
  • Removal of stimulus (negative feedback)
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16
Q

Hypothalamic-Pituitary-Adrenal (HPA) axis

Phys 35 Endocrine System General Concepts

A

Hypothalamus secrete CRH -> anterior pituitary secrete ACTH -> adrenal cortex secrete cortisol -> inhibit CRS and ACTH

CRH: corticotropin-releasing hormone
ACTH: adrenocorticotropic hormone

17
Q

Hyposecretion vs hypersecretion vs resistance

Disorder/dysregulation in endocrine system

Phys 35 Endocrine System General Concepts

A
  • Hyposecretion: secrete insufficient hormone
  • Hypersecretion: secrete excess hormone
  • Resistance: unresponsive to hormone (can lead to hyposecretion)
18
Q

Primary vs secondary vs tertiary endocrine pathology/deficiency

Phys 35 Endocrine System General Concepts

A
  • Primary: defect in target endocrine gland (adrenal cortex)
  • Secondary: defect in proximal regulator (pituitary) of target gland
  • Tertiary: defect in distal regulator (hypothalamus) of target gland
19
Q

Hormone levels in primary vs secondary vs tertiary endocrine pathology

Phys 35 Endocrine System General Concepts

A

Primary:
- Defect in adrenal cortex
- Low cortisol, high ACTH and CRH

Secondary:
- Defect in pituitary
- Low cortisol and ACTH, high CRH

Tertiary:
- Defect in hypothalamus
- Low cortisol, ACTH, CRH

20
Q

Bioassay test for cortisol hyposecretion

Phys 35 Endocrine System General Concepts

A
  • Stimulation test
  • Give ACTH to promote cortisol secretion
  • If cortisol increases -> HPA axis is intact
  • If cortisol remains low -> adrenal cortex or pituitary (loss of trophic effect of ACTH on adrenal cortex) is dysfunctional
21
Q

Bioassay test for cortisol hypersecretion

Phys 35 Endocrine System General Concepts

A
  • Suppression test
  • Give dexamethasone at midnight to suppress ACTH secretion -> prevents increase in cortisol in the morning
  • If cortisol is suppressed -> HPA axis is intact
  • If cortisol remains high -> adrenal cortex or pituitary is dysfunctional
22
Q

What are the regions of the adrenal gland? (2)

Phys 36 Adrenal Gland

A
  1. Adrenal cortex (outer region)
  2. Adrenal medulla (inner region)
23
Q

What are the layers of the adrenal cortex, from outer to inner layer? (3)

Phys 36 Adrenal Gland

A
  1. Zona glomerulosa
  2. Zona fasciculata
  3. Zona reticularis
24
Q

What hormones does each layer of the adrenal cortex secrete?

Phys 36 Adrenal Gland

A

Zona glomerulosa: mineralocorticoids (salt)
- Aldosterone

Zona fasciculata: glucocorticoids (sugar)
- Cortisol

Zona reitcularis: androgens (sex)
- Estrogen
- Testosterone

Sugar, salt, sex

25
Q

Aldosterone
- Site of synthesis
- Action
- Regulation

A
  • Made in zona glomerulosa of adrenal cortex
  • Increase blood vol/pressure by increasing reabsorption of sodium + excretion of potassium by kidney
  • Regulated by Renin-Angiotensin-Aldosterone system (RAAS)
26
Q

Hyperaldosteronism
- Cause
- Effects
- Example

A

Cause:
- Hypersecretion of aldosterone

Effects:
- Hypertension (reabsorption of Na+ -> increased blood vol + pressure)
- Hypokalemia (excretion of K+)

Example:
- Primary hyperaldosteronism (Conn’s syndrome)

27
Q

Cortisol
- Site of synthesis
- Action
- Regulation

A
  • Made in zona fasciculata of adrenal cortex
  • Increase blood glucose (by increasing insulin resistance and mobilising fuel), anti-inflammatory (decrease immune system function)
  • Regulated by hypothalamic-pituitary-adrenal (HPA) axis
28
Q

Metabolic effects of cortisol in:
- Liver
- Skeletal muscle
- Adipose tissue

A

Liver:
- Increase gluconeogenesis
- Increase glycogenolysis

Skeletal muscle:
- Decrease protein synthesis
- Increase protein degradation
- Decrease glucose uptake

Adipose tissue:
- Increase lipid degradation

Net result: mobilise fuel stores to increase plasma glucose

29
Q

Cortisol levels are (…) in the morning and (…) at night

A

Cortisol levels are highest in the morning and lowest at night

30
Q

Issues with excess use of cortisol

A
  • Bone breakdown: osteoporosis, avascular necrosis of joints, osteoarthritis
  • Insulin resistance: type 2 diabetes
  • Immune suppresion: increased risk of infections
31
Q

Cushing’s syndrome
- Cause
- Clinical features

A
  • Caused by excess cortisol (hypercortisolism)
  • Thinning of hair, facial plethora, dorsocervical and supraclavicular fat pads, weight gain, thin limbs with muscle atrophy, purple striae on abdomen due to thinning of skin

Cushing’s disease: dysfunction in pituitary gland (ACTH) specficially

32
Q

What are the levels of cortisol and ACTH in primary vs secondary Cushing’s syndrome?

A

Primary:
- High cortisol (due to overactive adrenal gland)
- Low ACTH (due to -ve feedback from cortisol)

Secondary:
- High cortisol
- High ACTH (due to overactive pituitary gland that does not respond to -ve feedback)

33
Q

Addison’s disease
- Cause
- Cortisol vs ACTH levels
- Clinical manifestations

A
  • AKA adrenal insufficency
  • Deficiency in all adrenal cortex hormones, especially glucocorticoids and mineralcorticoids (main source of androgens = gonads)
  • Low cortisol, high ACTH
  • Excess ACTH -> excess α MSH -> hyperpigmentation of skin
  • Deficient aldosterone + cortisol -> low Na+ and high K+ -> hyponatremia, hyperkalemia, hypotension, salt craving
34
Q

Catecholamines (epinephrine, norepinephrine, dopamine):
- Site of synthesis
- Action/metabolic effects

A
  • Made in adrenal medulla
  • Activate sympathetic system (fight or flight response)
    -> increase cardiac output
    -> constrict blood vessels to peripheral tissues and gut to increase oxygen delivery to muscles
    -> dilate smooth muscle in bronchi/bronchioles to increase oxygenation of blood
    -> inhibit insulin release to maintain blood glucose levels
    -> increase lipolysis in adipose tissue to raise blood glucose
35
Q

Pheochromocytoma
- Cause
- Clinical features

A
  • Caused by excess catecholamines
  • Five Ps: pain, pallor, palpitations, pressure (hypertension), perspiration
36
Q

What kind of cells comprise the thyroid gland?

A

Thyroid follicles
- Epithelium = single layer of cuboidal follicular cells
- Fluid filled space = colloid -> contains thyroglobulin

37
Q
A

Duke-NUS MS1 (12 decks)

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