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BioMed > Adrenal Axis > Flashcards

Adrenal Axis Flashcards

1
Q

structure of the hypothalamus

A

infundibulum (stalk)

anterior pituitary

posterior pituitary

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2
Q

structure of the pituitary gland

A

Pars Tuberalis

Pars Intermedia

Pars Distalis

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3
Q

overview of adrenal axis

A

Hypothalamus secretes Corticotropin releasing hormone (CRH)

CRH acts on anterior pituitary

then ant pit secretes Adrenocorticotropin hormone (ACTH) which acts on adrenal cortex

cortex secretes cortisol which functions as the negative feedback loop

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4
Q

CRH synthesis and release :

central stimulatory control

A

CRH is made in the hypothalamic paraventricular nucleus

Central stimulatory control :

  • noradrenergic
  • stimulates pre-proCRH gene and protein expression (196 AA)
  • processed to CRH (41 AA)
  • stimulates pulsatile release of CRH
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5
Q

CRH synthesis and release :

Inhibitory influences

A

physiological levels of cortisol inhibit release of CRH (and possibly inhibit pre-proCRH gene expression)

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6
Q

CRH background

A

CRH is produced by parvocellular neuroendocrine cells within the paraventricular nucleus of the hypothalamus

CRH is released at the median eminence (at the base of the brain) from their neurosecretory nerve terminals, into blood vessels in the hypothalamo-pituitary portal system

The blood vessels carry the CRH peptides to the anterior lobe of the pituitary, where it stimulates corticotropes to secrete adrenocorticotropic hormone

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7
Q

ACTH synthesis & release (anterior pituitary) :

POMC family

A

ACTH ( adrenocorticotropic hormone) : regulates adrenal cortex function

MSH (melanocyte stimulating hormone) : skin pigmentation in response to UV radiation

End (beta-endorphin) : analgesic roles in central nervous system

Enk (enkephalin) : analgesic roles in fetus

MC3,4,5 - receptors : hypothermia, hypotension, feeding behaviour, appetite

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8
Q

what are convertases

A

enzymes that cleave POMC

different convertases give rise to different products

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9
Q

what is the struture of the adrenal gland

A

like pituitary gland; has 2 embryological distinct tissues merged during development

Adrenal cortes = steroid factory

Adrenal medulla = modified sympathetic ganglia - secrete catecholamines

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10
Q

what is made in the adrenal cortex ?

A

Glucocorticoids

Mineralocorticoids

Sex Steroids

** THREE MAIN CLASSES OF STEROID HORMONES **

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11
Q

what is made in the adrenal medulla

A

catecholamines

epinepherine

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12
Q

anatomy of the adrenal gland

A

Connective Tissue Capsule

Adrenal Cortex :

  1. zona glomerulosa
  2. zona fasciculata
  3. zona reticularis

Adrenal medulla

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13
Q

where are glucocorticoids (cortisol [ACTH]) made

A

zona fasciculata

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14
Q

how is the glucocorticoid cortisol made

A

cholesterol is converted into pregnenolone (via enzymes of the inner mitochondria)

becomes 17-OH pregnenolone

becomes 17-OH progesterone

becomes 11-deoxycortisol

(via enzymes of the inner mitochondria) gives cortisol

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15
Q

how is corticosterone (dominant glucocorticoid in rodents) made

A

cholesterol

pregnenolone

progesterone

deoxycorticosterone

corticosterone

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16
Q

why is cortisol essential for life ?

A

Protects against hypoglycemia (low blood sugar)

Promotes gluconeogenesis (increase blood sugar)

Plays a role in immune system, bone, muscle

17
Q

cortisol and inflammation

A

cortisol as a natural regulator of the inflammatory response

> clinical use of glucocorticoids as anti-inflammatory agents

18
Q

negative effects of cortisol

A

causes breakdown of skeletal muscle (for gluconeogenesis)

suppresses immune system

catabolic on bone

affects brain function (mood, memory, learning)

19
Q

Cushing’s syndrome (primary)

A

High levels of corticosteroids in the blood cause Cushing’s Primary

  • prolonged exposure to high levels of cortisol. This can be caused by taking glucocorticoid drugs, or diseases that result in excess cortisol, ACTH or CRH levels
20
Q

Cushing’s disease (secondary)

A

A pituitary-dependent cause of Cushing’s syndrome: a tumor in the pituitary gland produces large amounts of ACTH, causing adrenals to make excess cortisol

21
Q

How do you distinguish Cushing’s syndrome (primary hypercortisolism) from Cushing’s disease (secondary hypercortisolism)

A

ACTH levels are lower in the syndrome form

22
Q

Effects of Cushing’s syndrome

A

causes changes in carbohydrate & protein metabolism, hypergycemia, hypertension, muscular weakness

Metabolic problems give rise to puffy appearance, CNS disorders (depression, decreased learning, memory, etc.)

23
Q

Treatment of Cushing’s syndrome

A
  • surgery to remove pituitary or adrenal gland (depending on which is causing it)
  • medical management of signs and symptoms (eg/ insulin for diabetes, anti-hypertensives for BP)

if not treated, disease worsens, overall health can deteriorate, especially worsening diabetes, high BP - that can lead to strokes or MI

24
Q

What is Addison’s disease ?

A

primary hypocortisolism

Adrenal insuffiency, many causes including genetic, autoimmune destruction of adrenal cortex

when acquired; high dose steroids >1 week begins to suppress adrenal glands by suppressing CRH and ACTH

25
Q
A
26
Q

Adrenal cortisol secretion

A

continuous, pulsatile, circadian rhythm

ie/ goes down when you go to bed and increases in the day

27
Q

what happens with insomnia

A

people with insomnia secrete more cortisol around sleep time

28
Q

PPID in horses

A

pituitary pars intermedia dysfunction

affects : older horses but has been diagnosed in horses and ponies as young as 10

cause (impaired pituitary gland) :

hyperplasia & hypertrophy of the pars intermedia of the pituitary gland

increased secretion of cortisol by adrenal glands

results in high blood glucose and suppression of the immune system

29
Q

what are the common signs of PPID in horses

A
  • Hypertrichosis (excessive hair growth)
  • Abnormal hair coat including patches of long hair on the legs, wavy hair on the neck, changes in coat colous
  • muscle atrophy
  • excessive sweating
  • formation of fat pads on top of the neck, tail and above and around the eyes
  • pot-bellied appearance
30
Q

how do you diagnose and treat PPID in horses ?

A

Diagnosis : measuring basal ACTH & fasting insulin

Treatment :

Drug - Pergolide; acts on the pituitary gland to decrease circulatinh ACTH

Management - exercise, weight loss (if obese), limit starch/sugar in horse’s diet

BioMed (10 decks)

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