Endocrine Disorders

Question 1

Draw or illustrate the hypothalamic-pituitary-thyroid axis with the major hormones involved?

Answer 1

VD

Question 2

What is the difference between primary (1 o) and secondary (2 o) conditions?

Answer 2

• Primary = Directly affects or is due to the organ or gland in the disorder
• Secondary = Problems are due to a secondary problem - not the major organ or gland in disorder

Question 3

State the levels of T3/T4 and TSH in primary and secondary Hyperthyroidism in L/N/H? VD

Answer 3

• If your thyroid isn’t producing enough hormones, the pituitary gland will boost TSH to increase thyroid hormone production
• High TSH levels indicate hypothyroidism

Question 4

Draw or illustrate the hypothalamic-pituitary-adrenal axis with the major hormones?

Answer 4

VD

Question 5

What two components should be looked at when measuring endocrine disorders?

Answer 5

• Measure hormone levels: Are they appropriate depending on the current physiological state?
• Is the endocrine tissue functional?: Dynamic tests of endocrine function

Question 6

State 3 examples of adrenal steroids?

Answer 6

• Mineralcorticoids: Aldosterone
• Glucocorticoids: Cortisol
• Adrenal androgens

Question 7

What is the disorders for aldosterone and cortisol excess called?

Answer 7

• Aldosterone excess = Conn’s syndrome / primary hyperaldosteronism
• Cortisol excess = Cushing’s syndrome (either primary or secondary)
• Cushing’s syndrome is primarily due to tumour of anterior pituitary

Question 8

What is aldosterone secretion activated by?

Answer 8

• RAAS
• Increased K+

Question 9

What is RAAS activated by and describe the mechanism behind this?

Answer 9

• RAAS primarily measures fall in blood volume which is activated and characterised by:
• Reduced renal perfusion (due to ‹ BP)
• Increased sympathetic activity
• VD for mechanism. Actually a really good diagram

Question 10

How are aldosterone levels maintained?

Answer 10

Aldosterone = Increase Na+ reabsorp. -> Increased H20 reabsorp. -> Increased ECF volume -> Increased BV/BP and therefore maintenance of blood volume

Question 11

What is used in the diagnosis of primary hyperaldosteronism?

Answer 11

• Plasma aldosterone/ renin ratio
• Should be high ald. / low renin

Question 12

If excess aldosterone is caused by aldosterone-secreting adenoma (adrenal), What effect will it have on RAAS activation?

Answer 12

• Hypertension, hypokalaemia induced
• Aldo. action = Increased Na+ reabsorp. -> Increased H20 reabsorp. -> Increased ECF volume -> Increased BV/BP and therefore maintenance of blood volume
• Lead to minimal activation of RAAS due to increase in perfusion + Na+ conc. in distal tube leading to higher volume

Question 13

If excess aldosterone is caused by secondary hyperaldosteronism e.g. renal artery stenosis, what effect will it have on ald.:renin ratio?

Answer 13

• Renal artery stenosis - Blockage of kidney - decrease in perfusion pressure = RAAS activation
• High ald. : High renin

Question 14

What is the most common cause of cushing’s syndrome/hypercortilosim and state what can occur?

Answer 14

Common cause = iatrogenic -> consequence of medical therapy e.g. drugs

Question 15

State the effects of Cushing syndrome

Answer 15

• Exogenous glucocorticoids activate cortisol receptor
• At high doses will shut down HPA - Lowered natural cortisol + androgens produced
• Adrenal cortex atrophies with lack of ACTH stimulation
• Several days may be required for adrenal to become responsive to ACTH again
• VD

Question 16

What is cushing’s disease and state the major findings in terms of hormones?

Answer 16

• Excess cortisol due to ACTH-secreting pituitary adenoma
• It’s a cause of Cushing’s syndrome

Question 17

What can be an additional cause of cushing’s syndrome and state the major findings in terms of the hormones?

Answer 17

• Ectopic ACTH source
• View diagram

Question 18

What test is used to diagnose cushing’s syndrome and describe its mechanism of action?

Answer 18

• Dexamethasone suppression test
• Inhibits hypothalamus + pituitary gland to reduce CRH + ACTH levels
• Leads to the Suppression of cortisol levels

Question 19

State whether suppression happens at low dose, high dose and plasma ACTH for conditions of cushing’s syndrome when diagnosing it? (3)

Answer 19

VD

Question 20

What is Addison’s disease?

Answer 20

Primary adrenal insufficiency -> Insufficient cortisol + aldosterone levels

Question 21

What are the 5 clinical features of Addisons disease?

Answer 21

• Hypotension
• Plasma [Na+]: normal to low
• Plasma [K+]: normal to high
• High ACTH
• Elevated plasma renin
• May be unmasked by significant stress or illness - shock, hypotension, volume depletion (adrenal crisis)

Question 22

What is the hallmark for addison’s disease and what can be used for diagnosis?

Answer 22

• Hallmark is high ACTH, low cortisol
• Progressive, but can eventually lead to adrenal crisis - fatal if not treated
• ACTH stimulation test can aid diagnosis: assess ability of adrenal to produce cortisol in response to ACTH
• Short or long synacthen test -> Synacthen = synthetic ACTH

Question 23

Describe the short synacthen test with the specific ranges and values?

Answer 23

• Measure baseline cortisol (9am) and 30 min after 250 ug synacthen (synthetic ACTH) i.m.
• Adrenal insufficiency is excluded by an increase in cortisol of >200 nmol/L and/or a 30 min value >550

Question 24

Describe the long synacthen test with the specific ranges and values?

Answer 24

• Adrenal cortex ‘shuts down’ in absence of stimulation by ACTH - time needed to regain responsiveness
• 3-day stimulation with synacthen
• In secondary (but not primary) adrenal insufficiency cortisol increases by >200 mol/L over baseline
• Long test not often necessary since ACTH assay can distinguish
• ACTH assay = Measures levels of cortisol + ACTH in blood