Cushing's syndrome is associated with increased ACTH and is also characterized by?

Cushing's syndrome, particularly when it is associated with increased levels of ACTH, typically results from a pituitary adenoma or ectopic ACTH production. This condition leads to excessive cortisol production, which has a variety of systemic effects.

One of the notable effects of elevated ACTH is hyperpigmentation. ACTH has a similar structure to melanocyte-stimulating hormone (MSH), which is responsible for the stimulation of melanocytes in the skin to produce melanin. Consequently, in patients with Cushing's syndrome due to increased ACTH, you often observe a characteristic darkening of the skin, especially in areas subject to friction or areas exposed to sunlight. This hyperpigmentation is due to the overproduction of melanin and can manifest distinctly, particularly in the palms, gums, and other areas.

In contrast, the other choices do not align with the typical manifestations of Cushing's syndrome caused by elevated ACTH. Hypopigmentation is generally not a feature of this syndrome; rather, it may be associated with conditions that diminish melanin production. Hypoglycemia is also unlikely, as Cushing's syndrome often causes hyperglycemia due to cortisol's role in increasing gluconeogenesis. Hypercalcemia does not relate specifically to