Question on the endocrine system

[mpelter]

Hi everyone,

Since the next exam is coming up soon, I decided to post a question on the endocrine system as well.

 

Cushing’s syndrome, also known as hypercortisolism, can be caused either by a tumor of the anterior pituitary or a tumor of the adrenal cortex.

 a) How could these possibilities be distinguished by measuring levels of ACTH and cortisol in the blood?

 b) How would blood levels of cortisol change after administering a dose of dexamethasone (a synthetic glucocorticoid) to a person with Cushing’s syndrome, compared to a normal person? Briefly explain both answers.

It’s good if you are able to understand the symptoms of the diseases described in class and apply them to graphs or given scenarios (or contrast them as above). I'll post the answer on Friday

 

Email me with responses or questions!

Megan

 

 

[mpelter]

 Hi everyone!

Thanks to the people who emailed me their responses! Here is the answer to this question:

a)      In Cushing’s caused by an anterior pituitary tumor, levels of both cortisol and ACTH would be high, because the ACTH-secreting pituitary cells would not be subject to negative feedback regulation by circulating cortisol. In Cushing’s caused by an adrenal cortex tumor, levels of cortisol would be high but levels of ACTH would be low, because the high cortisol would suppress secretion of ACTH from the normal pituitary.

 

b)      Administration of dexamethasone would have little effect on the high blood levels of cortisol in a person with Cushing’s because dexamethasone would not suppress cortisol secretion. Administration of dexamethasone to a normal person would lower cortisol levels, due to negative feedback suppression of cortisol secretion.

 

From the responses sent, I think that an important thingto remember is to indicate distinctly what you are talking about (for example, in part A which tumor causes what level of ACTH and cortisol).

If you have any questions, feel free to email me

Megan