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32 Cards in this Set
- Front
- Back
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What are the 3 hormones in the HPA axis? What is the source of each?
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-CRH from the hypothalamus
-ACTH from the pituitary -Cortisol from the adrenal |
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What test is done for diagnosis of adrenal insufficiency and 21-OHase deficiency?
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ACTH stimulation test
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What test is done for diagnosis of Cushing's syndrome?
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CRH test
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From what nuclei in the hypothalamus is CRH made?
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Paraventricular nuclei PVN
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What does CRH do?
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Stimulates release of ACTH from the pituitary
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What actions does ACTH have?
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1. Tropic - stimulates cortisol secretion from adrenal cortex
2. Trophic - stimulates growth and function of the adrenal gland |
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What inhibits CRH and ACTH production?
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Neg feedback from cortisol
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What are 2 things that can cause adrenal insufficiency (AI)?
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-Primary adrenal problem due to autoimmune dmg or TB
-Secondary pituitary problem - ie hypopituitarism |
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What test will diagnose AI?
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ACTH injection/Cosyntropin
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What will the adrenal response to Cosyntropin/ACTH injection be if there is Adrenal insufficiency?
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Primary - no cortisol release
Secondary - subnormal release |
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Is the Cosyntropin/ACTH test very good at differentiating btwn primary vs secondary AI?
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No - there is significant overlap between the two entities
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Why is the response to ACTH stimulation subnormal if AI is due to hypopituitarism and low ACTH?
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Because of the lack of trophic stimulation to keep the adrenal gland plump and functioning.
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What is the best way to differentiate primary vs secondary adrenal insufficiency?
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Look at PLASMA ACTH levels
Primary: ACTH will be high Secondry: ACTH will be low |
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What else is ACTH stimulation test used for diagnosing other than primary/secondary AI?
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21-hydroxylase deficiency
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What is 21-hydroxylase normally responsible for in the adrenals?
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Conversion of 17-OHprogesterone to 11-deoxycortisol
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What happens when 21-hydroxylase is deficient?
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There are high levels of 17-OH progesterone
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What are the basal levels of 17-OHprogesterone in homo vs heterozygotes for 21-hydroxylase mutations?
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Homo: elevated 17-OHprogesterone
Hetero: normal levels |
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What are the levels of 17-OHprogesterone in homo vs heterozygotes when stimulated with ACTH?
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Both will be elevated
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What symptoms develop in patients with 21-hydroxylase deficiency? Why?
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Virilism - because the increased 17-OHprogesterone gets shunted into the androgen pathway
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What test is used to differentiate the cause of Cushing's syndrome (ectopic tumor vs Cushings disease, etc)?
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CRH stimulation test
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What are basal ACTH levels in:
-Cushings disease -Ectopic ACTH tumor -Adrenal tumor |
CD: high
Ectopic: high Adrenal tumor: low |
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What is cushing's disease?
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An ACTH-secreting pituitary adenoma
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How will ACTH production from the pituitary change when CRH is injected in:
-Cushings disease -Ectopic ACTH tumor -Adrenal tumor |
CD: increase even higher
Ectopic: no change (tho there is a caveat) Adrenal tumor: no change |
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How could ACTH levels change in response to CRH stimulation if the source is an ectopic lung tumor?
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Some bronchial carcinomas retain CRH receptors
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What is the best use of the CRH stimulation test?
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To determine if elevated cortisol is due to Cushing's disease/Ectopic tumor, versus Adrenal tumor.
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What is the best way to differentiate between Cushing's disease and an Ectopic tumor?
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Inferior petrosal sinus sampling
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What does inferior petrosal sinus sampling (IPS) allow you to determine?
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The amount of ACTH draining from the pituitary after CRH injection.
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What will IPS sampling results be for CRH stimulation in the case of an Ectopic tumor secreting ACTH?
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A low ratio of ACTH in the inf petrosal sinus : plasma; because CRH won't stimulate any increase from the pituitary - it's not the source.
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What will IPS sampling results be for CRH stimulation in the case of Cushing's disease?
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The IPS:P ratio of ACTH will be greatly elevated because NOW the pituitary IS the source and CRH will exaggerate production.
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So what is the IPS:P ratio of [ACTH] in
-Cushing's disease -Ectopic tumor secreting ACTH |
CD: >3
Ectopic: <2 |
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What are basal ACTH levels in
-Primary adrenal insufficiency -2ndary AI -Tertiary AI |
1: HIGH (no neg fback)
2: low (pituitary's not working) 3: low (no CRH) |
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What will be the change in ACTH in response to CRH injection for
-Primary AI -2ndry AI -Tertiary AI |
1: ACTH will increase even higher
2: no change - the pituitary's still not working 3: May increase some |
