question about question on uworld (HPA axis)

[axeon123]

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I have this question - patient had been on chronic corticosteroid therapy, and she underwent minor surgical procedure, then she experienced symptoms of lack of cortisol. And they ask what changes would be seem in CRH/ACTH/cortisol. I picked +CRH, +ACTH, and -cortisol because I assume steroids inhibit CRH/ACTH secretion, so the adrenal undergoes atrophy from understimulation. But the answer was decreased everything. If she is still taking corticosteroids, then it makes sense for everything to be down, and symptoms occur because this steroid level is not enough. And in stress, you need more cortisol. But why would CRH/ACTH not increase? Is the H and P atrophied, too? If the corticosteroid she is taking is not enough, shouldn't the body upregulate CRH/ACTH?

 

[Dirt]

I have this question - patient had been on chronic corticosteroid therapy, and she underwent minor surgical procedure, then she experienced symptoms of lack of cortisol. And they ask what changes would be seem in CRH/ACTH/cortisol. I picked +CRH, +ACTH, and -cortisol because I assume steroids inhibit CRH/ACTH secretion, so the adrenal undergoes atrophy from understimulation. But the answer was decreased everything. If she is still taking corticosteroids, then it makes sense for everything to be down, and symptoms occur because this steroid level is not enough. And in stress, you need more cortisol. But why would CRH/ACTH not increase? Is the H and P atrophied, too? If the corticosteroid she is taking is not enough, shouldn't the body upregulate CRH/ACTH?

From Greenspan's clinical endocrinology

Stress Responsiveness
Plasma ACTH and cortisol secretion are also characteristically responsive to physical stress. Thus, plasma ACTH and cortisol are secreted within minutes following the onset of stresses such as surgery and hypoglycemia, and these responses abolish circadian periodicity if the stress is prolonged. Stress responses originate in the central nervous system and increase hypothalamic CRH and thus pituitary ACTH secretion. Stress responsiveness of plasma ACTH and cortisol is abolished by prior high-dose glucocorticoid administration and in spontaneous Cushing's syndrome; conversely, the responsiveness of ACTH secretion is enhanced following adrenalectomy. Regulation of the HPA axis is linked to that of the immune system. For example, interleukin-1 (IL-1) stimulates ACTH secretion, and cortisol inhibits IL-1 synthesis.

 

[donkeyboy]

chronic corticosteroid therapy --> loss of ACTH secretion (ie. it won't bounce back abruptly)

if she's just out of surgery she'll have an adrenal crisis because the corticosteroids were stopped abruptly and her pituitary is not compensating, thus decrease in everything

 

[axeon123]

what about the hypothalamus secreting CRH - it just gets knocked out, too? because I am thinking if the hypothalamus + pituitary is being suppressed, shouldn't there be some increase?

 

[mordounhas]

The previous high-dose steroids basically shut down the axis for a while. The surgery imposed an additional stress, so the patient was deficient in cortisol, but the hypothalamus and pituitary haven't had sufficient time to recover, so they can't react to the low cortisol levels yet. This is why they always talk about tapering steroid off (otherwise, the plasma cortisol levels basically dive off a cliff and nothing is there to help produce more for a while). I couldn't find a decent timeline for how long it takes it to re-establish itself while quickly looking, but definitely more than a day or two. Hence the patient's problems.

One more thing- if the levels of CRH and ACTH were really low (as you'd expect in a patient like this), even if the pituitary and hypothalamus increased their levels of CRH and ACTH production immediately, it would take a while to reach the levels you'd expect to see in a normal patient. I'm not sure if you'd see an increase in CRH and ACTH in that patient that soon after steroid withdrawal, but regardless, it wouldn't be enough of an increase to raise it to normal or increased levels.

 

[turkeyjerky]

agree with above, it definitely takes a while, I'm thinking about a week or so, for the HPA axis to rev up

One more thing- if the levels of CRH and ACTH were really low (as you'd expect in a patient like this), even if the pituitary and hypothalamus increased their levels of CRH and ACTH production immediately, it would take a while to reach the levels you'd expect to see in a normal patient. I'm not sure if you'd see an increase in CRH and ACTH in that patient that soon after steroid withdrawal, but regardless, it wouldn't be enough of an increase to raise it to normal or increased levels.

Actually, I don't think that's correct. ACTH is a peptide hormone and is degraded rapidly, moreover it's released in a pulsatile manner, as are all anterior pituitary hormones, which is why it's difficult to interpret an ACTH level in a patient.

 

[axeon123]

Thanks for the replies. Blah, this sounds like a fact I have to memorize. Adrenal atrophy makes sense why there is no cortisol output. But the hypothalamus/pituitary, guess I'll just have to remember that...