A 54-year-old woman presents with abdominal pain and dark pigmentation of skin. What is the most likely electrolyte abnormality expected?

The presentation of abdominal pain and dark pigmentation of the skin in this 54-year-old woman suggests a possible diagnosis of primary adrenal insufficiency, also known as Addison's disease. One of the hallmark features of this condition is the disruption of adrenal hormone production, particularly cortisol and aldosterone.

In cases of adrenal insufficiency, there is decreased secretion of cortisol, which normally helps maintain blood pressure and manage stress, and aldosterone, which is crucial for sodium retention and potassium excretion. With low aldosterone levels, the kidneys are unable to retain sodium, leading to hyponatremia (low sodium levels) and an inability to excrete potassium, resulting in hyperkalemia (high potassium levels).

Thus, the expected electrolyte abnormality in this scenario would be characterized by low sodium and high potassium levels, correlating with option B. The clinical picture of dark pigmentation also supports this diagnosis, as increased levels of adrenocorticotropic hormone (ACTH) in response to low cortisol can lead to increased melanin production, causing the observed skin pigmentation changes.

Understanding these mechanisms is crucial for recognizing the signs and symptoms associated with adrenal insufficiency and interpreting electrolyte disturbances in this context.