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Y2 - ENDO > Hypoadrenal Disorders > Flashcards

Hypoadrenal Disorders Flashcards

1
Q

What are the 3 parts of the steroid biosynthetic pathway?

A
  1. Mineralocorticoid
  2. Glucocorticoid
  3. Sex steroids
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2
Q

1) What enzyme converts cholesterol into pregnenolone and how?
2) Where is this enzyme located?

A

1) CY P450 SCC - performs side chain cleavage
2) In the zona glomerulosa of the adrenal gland

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3
Q

Where within the adrenal glands would you find the enzymes for and go down the glucocorticoid part of the steriod biosynthetic pathway?

A

Zona fasciculata

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4
Q

What is chemically involved in the conversion of cholesterol into pregnenolone?

A

Side chain cleavage by CYP450 CC and hydroxylation at position 3

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5
Q

Outline the hypothalamo-pituitary-adrenal axis

A
  1. Hypothalamus secretes CRH
  2. Pituitary secretes ACTH
  3. Adrenal secretes cortisol
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6
Q

How does stress precipitates cortisol production?

A
  1. Pituitary detects stress
  2. Pituitary secretes ACTH in response
  3. Adrenal secretes cortisol in response to ACTH
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7
Q

Outline the steroid biosynthetic pathway (write it down on paper)

A

Also note there should be conversion of corticosterone to aldosterone by 18- something hydroxylase

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8
Q

Give the 3 causes of adrenocortical failure and specify which of these is the most common worldwide and in the UK?

A
  1. Tuberculosis Addison’s Disease - most common worldwide
  2. Autoimmune Addison’s Disease - most common in UK
  3. Congenital Adrenal Hyperplasia
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9
Q

List 8 clinical features of Addison’s disease and explain why these occur where possible

A
  1. HOTN, potentially leading to death due to severe HOTN. Due to hypoaldosteronism
  2. Hyponatraemia - loss of sodium in urine due to hypoaldosteronism (so less sodium reabsorption)
  3. Hyperkalaemia - increased K+ in blood due to hypoaldosteronism so less K+ excretion
  4. Hypoglycaemia - due to lack of glucocorticoid hormones
  5. Hyperpigmentation - due to XS POMC → ACTH conversion and thus lots of MSH causing pigmentation
  6. Vitiligo patches - autoimmune disease of the skin
  7. Emaciation / vomiting and diarrhoea
  8. Muscle weakness
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10
Q

Explain why there is hyperpigmentation in Addison’s disease

A
  • Lack of cortisol
  • So lack of negative feedback on ACTH
  • So XS ACTH production
  • So more POMC → ACTH + MSH conversion
  • MSH causes pigmentation
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11
Q

Give 2 ways to test for Addison’s

A
  1. Measure cortisol and ACTH at 9am in the morning. Cortisol should be high then due to diurnal rhythm of its secretion. If its low at that time then this is indicative of Addisons. Low cortisol so little negative feedback on ACTH so high ACTH.
  2. 250mg IM Synacthen (synthetic ACTH) injection at 9am - this should stimulate cortisol release in normal people but if there is an absent cortisol response, this is indicative of Addison’s - will be 100 when normal people will have >600 after half an hour
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12
Q

What are the commonest causes of complete adrenal hyperplasia?

A
  • Complete 21-hydroxylase deficiency
  • Partial 21-hydroxylase deficiency
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13
Q

What is complete 21-hydroxylase deficiency - what are its signs and how does it cause its signs pathophysiologically?

A
  • LOW ALDOSTERONE AND CORTISOL AND HIGH SEX STEROIDS
  • XS testosterone due to accumulation of 17-hdyroxyprogesterone which is converted into androstenedione (a precursor to testosterone) → virilisation in girls due to testosterone → genital ambiguity in girls
  • Addisonian crisis and loss of consciousness due to hypoaldosteronism causing hyponatraemia
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14
Q

How to treat Addisonian crisis in complete 21 hydroxylase deficiency?

A
  • Saline for the hyponatraemia
  • Hydrocortisone and fludrocortisone to replace aldosterone, keeping them alive
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15
Q

What sign of complete 21-hydroxylase deficiency exists in neonate girls that does not exist in boys and why? This causes the condition to go undetected in neonate boys

A
  • Virilisation leading to genital ambiguity due to XS testosterone (due to XS 17-hydroxyprogesterone and thus androstenedione and thus testosterone)
  • This is undetected in male neonates because the testosterone does not affect male genitalia adversely (it uses testosterone anyway)
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16
Q

Why does complete 21-hydroxylase deficiency not affect the foetus?

A

Becuase the missing enzyme (21-hydroxylase) is provided in the mother’s blood

17
Q

What is the difference in the clinical signs of partial 21-hydroxylase deficiency compared to complete 21-hydroxylase deficiency and explain this?

A
  • Low aldosterone and cortisol but not completely absent as in complete 21-hydroxylase deficiency so NO addisonian crisis
  • XS testosterone still though and due to later presentation (in later life not starting to present mainly in neonates). This leads to hirsutism and virilisation in females and precocious puberty in males
18
Q

1) What is the inheritance pattern of 11ß-hydroxylase deficiency?
2) Explain the pathophysiology of having 11ß-hydroxylase deficiency
3) What are the signs of 11ß-hydroxylase deficiency?

A

1) Recessive

2)

  • Low aldosterone and cortisol
  • BUT…
  • XS 11-hydroxycorticosterone which is a mineralocorticoid which acts like aldosterone
  • So apparent hyperaldosteronism despite actual hypoaldosteronism
  • Also XS sex steroids - XS testosterone

3)

  • HTN and HYPOKALAEMIA - due to the MR action of 11-hydroxycorticosterone
  • VIRILISATION - due to XS testosterone
19
Q

1) What is the inheritance pattern of having 17-hydroxylase deficiency?
2) Explain the pathophysiology of having 17-hydroxylase deficiency
3) What are the clinical signs of 17-hydroxylase deficiency?

A

1) Recessive

2)

  • XS mineralocorticoid pathway but lack of glucocorticoid and sex steroid pathway
  • Because you get accumulation of progesterone which because there’s no conversion into 17-hydroxyprogesterone
  • So mineralocorticoid pathway via progesterone precursor goes along nicely
  • Whereas due to lack of 17-hydroxyprogesterone, there is less glucorticoid or sex steroid development as this is an immediate precursor to these pathways

3)

  • HTN and HYPOKALAEMIA due to hyperaldosteronism
  • HYPOGLYCAEMIA due to lack of glucocorticoids
  • SUSCEPTIBLE TO INFECTION due to lack of cortisol
20
Q

2 investigations to test for 21-hydroxylase deficiency?

A
  1. Measure 17-hydroxyprogesterone levels
  2. Give Synacthen (synthetic ACTH) and they will still have low cortisol despite it

Y2 - ENDO (18 decks)

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