17 - Adrenal Glands Flashcards

1
Q

Where are the adrenal glands found, what is their structure and what do they produce and secrete?

A
  • Cap the upper part of the kidneys and like against the diaphragm
  • 6-8g combined
  • CT capsule has capsular plexus of blood vessels
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2
Q

What is the embryological origin of the adrenal glands?

A

- Medulla: neural crest cells that migrate into developing medulla

- Cortex: mesoderm

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3
Q

What are the corticosteroids released from each part of the adrenal glands?

A
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4
Q

Where are steroid hormones produced, what from, and how do they act on their target tissues?

A
  • Gonads and adrenal glands from cholesterol
  • Bind to nuclear receptors to modulate gene transcription
  • Glucocorticoids, mineralcorticoids, androgens, oestrogens, progestins
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5
Q

What type of hormone is adolsterone, where is it produced, what is it carried by in the blood and what action does it have?

A
  • Controls rate at which Na ions are reabsorbed

- Prime regulator of blood pressure

  • Upregulates sodium pump and ENaC in the collecting duct and colon
  • Part of RAAS
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6
Q

Briefly explain the process of the renin-angiotensin-aldosterone system and what the outcome is?

A
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7
Q

What are the two classes of hyperaldosteronism and how can they be distinguished between one another?

A
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8
Q

What are the signs of hyperaldosteronism and how can it be treated?

A
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9
Q

What is the structure of cortisol and what controls it’s secretion?

A
  • Glucocorticosteroid synthesised and released from zona fasiculata in response to ACTH
  • Negative feedback to hypothalamus to inhibit CRH and ACTH release
  • Steroid transported by transcortin (and albumin) and synthesised from cholesterol
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10
Q

What is CRH secreted in response to?

A

Secreted from hypothalamus in response to:

  • Physical (temp and pain) stressors
  • Emotional stressors
  • Chemical stress (hypoglycaemia)
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11
Q

How does blood cortisol vary at different times in the day?

A
  • Peak at about 7am and trough at 7pm so time should be noted when taking cortisol measurement and repeat measurements should be taken at the same time
  • Therefore, ACTH follows the same pattern
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12
Q

What actions does cortisol have on its target tissues?

A
  • Increased protein breakdown in muscle, lipolysis in fat, gluconeogenesis in liver
  • Anti-inflammatory effects
  • Depression of immune system
  • Decrease aa uptake
  • Decrease glucose uptake
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13
Q

What can cortisol be used for clinically?

A

- Medication for allergic reactions: prevents macrophage activity and mast cell degradation

- Anti-rejection for organ transplants: depresses immune system

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14
Q

What is the precursor of ACTH and what is the process by which it is synthesised?

A
  • Pro-opiomelanocortin (POMC)
  • Post translocational processing of POMC leads to ACTH, alpha-MSH and ADH
  • a-MSH present in ACTH sequence so in excess of ACTH there is some a-MSH activity
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15
Q

How does ACTH cause the secretion of cortisol?

A
  • ACTH is a peptide hormone
  • Binds to high affinity receptors on surface of cells in ZF and ZR
  • Activates cholesterol esterase increasing conversion of cholesterol esters to cholestrol
  • Binds to GPCR called melanocortin receptor (MC2) which uses CAMP as a second messenger. Differrent receptor to steroid hormones
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16
Q

What are the clinical consequences of excess ACTH secretion?

A
  • Increased pigmentation
  • Adrenal hyperplasia
  • Overproduction of cortisol
17
Q

Why are all corticosteroids transported by plasma proteins?

A

They are lipophillic

18
Q

What is phaeochromocytoma and what are the symptoms?

A
  • Overproduction of adrenaline by the adrenal medulla usully due to a chromaffin cell tumour
  • Secretes mainly noradrenaline
  • Life threatening hypertension
19
Q

How does the adrenal medulla link the neuro and endocrine systems and how does it synthesise what it secretes?

A
  • Secretes catecholamines
  • They are stored in chromaffin cells vesicles before being released into the blood stream
20
Q

When is adrenaline released and what effect does it have on the body?

A

Flight, fright or fight response

21
Q

Where are androgens secreted from and what do they promote?

A
22
Q

Where are the different adrenergic receptors found and what action do they have when stimulated?

A
23
Q

How does adrenaline act as a positive chronotrope?

A
24
Q

What drug can be given to a patient with hypertension from overactive RAAS?

A
  • ACE inhibitors
  • Angiontensin receptor blockers
  • Inhibitors of renin as an enzyme
25
Q

Compare the two types of hormones released from the adrenal glands in terms of their structure, their synthesis and their action, also include what a patient would need if they had a bilateral adrenalectomy.

A