Final answer:
The best screening test for Addison's disease is a blood test to measure the levels of cortisol and ACTH in the body.
Step-by-step explanation:
The symptoms described in the question, including weakness, hypotension, weight loss, hyperpigmentation, increased potassium levels, decreased sodium levels, and decreased pH, are consistent with a condition called Addison's disease.
Addison's disease is a rare disorder that results from the hyposecretion of corticosteroids, specifically adrenal insufficiency. The best screening test for Addison's disease is a blood test to measure the levels of cortisol and adrenocorticotropic hormone (ACTH) in the body.