The presence of dark pigmentation of the skin along with postural hypotension is most indicative of which disease?

The combination of dark pigmentation of the skin and postural hypotension is highly indicative of Addison's disease, which is also known as primary adrenal insufficiency. This condition arises from inadequate production of adrenal hormones, particularly cortisol, due to damage to the adrenal glands.

In Addison's disease, the lack of cortisol leads to a compensatory increase in adrenocorticotropic hormone (ACTH) from the pituitary gland. ACTH not only stimulates cortisol production but also has a stimulating effect on melanocytes, the cells responsible for skin pigmentation, leading to the characteristic hyperpigmentation observed in affected individuals.

Postural hypotension in Addison's disease occurs because the deficiency in mineralocorticoids (like aldosterone), which are responsible for sodium retention and fluid balance, results in volume depletion. When a person stands up, the lack of adequate fluid volume leads to decreased blood pressure, causing postural hypotension.

This clinical presentation of skin pigmentation and postural hypotension does not typically occur in the other conditions listed. Conn's syndrome primarily involves hypertension due to excess aldosterone without significant skin changes. Acromegaly is marked by excess growth hormone and changes in facial features and soft tissues, while Cushing's syndrome, which is associated with excess cortisol