Probably adrenal insufficiency

The morning cortisol is low and the ACTH is quite high (results repeated below). These findings are consistent with failure of the adrenal cortex to produce adequate cortisol, leading to decreased negative feedback on the anterior pituitary and increased ACTH output.

                       Patient    Reference
ACTH (P)              100 pg/ml    10 - 50
Cortisol 0800 hr (S)   10 ug/dl    12 - 26
Aldosterone (P)         7 ng/dl     7 - 24

Note that aldosterone is borderline low in a setting where sodium is low and the patient is showing signs of hypovolemia (i.e., orthostatic hypotension). This is distinctly abnormal (aldosterone should be high under these conditions) and this finding indicates an inadequate response in multiple adrenal cortical pathways.

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