The patient described above displays clinical symptoms consistent with Addison disease. Along with weight loss, weakness, hypotension, and hyperpigmentation, hyperkalemia is a common clinical finding.
Addison disease, or primary adrenal insufficiency, results from an inability of the adrenal cortex to synthesize and secrete glucocorticoid and mineralocorticoid hormones (primarily cortisol and aldosterone). One cause of Addison disease is autoimmune destruction of the adrenal cortex. A decrease in aldosterone (a mineralcorticoid) results in reduced sodium REABSORPTION and potassium SECRETION in the kidneys. This leads to hyponatremia and hyperkalemia, respectively.
In a review of autoimmune polyglandular syndrome, Majeroni et al. report that adrenal insufficiency should be diagnosed using the cosyntropin (Cortrosyn) test. Cosyntropin (Cortrosyn) is a synthetic derivative of adrenocorticotropic hormone (ACTH). In patients with low cortisol levels or symptoms of adrenocortical insufficiency, a failure of serum cortisol levels to increase after administration of cosyntropin makes a diagnosis of primary adrenocortical insufficiency more likely.
As discussed by Ismail, secondary adrenal insufficiency, also known as Addison SYNDROME, results from impaired stimulation of the adrenals due to abnormal adrenocorticotropin hormone and corticotropin-releasing hormone secretion from the hypothalamus and pituitary gland.
Illustration A depicts the hypothalamus-pituitary-adrenal axis. In primary adrenal insufficiency, the adrenal cortex is unable to produce cortisol (and aldosterone) no matter how high levels of ACTH.
Illustration B depicts the hyperpigmentation in the oral mucosa seen in Addison's disease.
Answer 1: A decrease in cortisol levels is consistent with a decrease in gluconeogenesis and therefore hypoglycemia.
Answer 3: A decrease in aldosterone would be expected to result in hyponatremia.
Answer 4: Central obesity is more consistent with Cushing's syndrome (hypercortisolism).
Answer 5: Pretibial myxedema is more consistent with Graves' disease.
Majeroni BA, Patel P. Autoimmune polyglandular syndrome, type II. Am Fam Physician. 2007 Mar 1;75(5):667-70. Review. PubMed PMID: 17375512.
PMID:17375512 (Link to Abstract)
Ismail AA. On the diagnosis and investigation of adrenal insufficiency in adults. Ann Clin Biochem. 2010 Jan;47(Pt 1):97-8. doi: 10.1258/acb.2009.009224. Epub 2009 Dec 1. PubMed PMID: 19952035.
PMID:19952035 (Link to Abstract)