To determine the efficacy of bilateral inferior petrosal sinus sampling in differentiating Cushing disease from ectopic Cushing syndrome.

Management of endogenous Cushing syndrome is based on its aetiology. Increased Adrenocorticotropic Hormone (ACTH) levels are the most common cause of this disorder and, therefore, it is critical to determine the source of ACTH before further management. Dynamic post contrast MRI is currently the most common investigation implied to diagnose pituitary adenoma; however, it comes with the drawback of low specificity and high false positive results.

Challenges in diagnosis of disease reported 100 years back: Cushing syndrome; recent advances.

Treatment of Cushing syndrome depends on diagnosis of etiology responsible for hypercortisolism in the body, which sometimes presents with a challenge. Inferior petrosal sinus sampling for ACTH levels, followed by peripheral venous sampling is a proven tool to be a gold standard for differentiating between peripheral and central cause of ACTH dependent Cushing syndrome. This case report is of an elderly female who presented as an outpatient in the endocrinology clinic of Aga Khan university hospital on 22/6/2017 with clinical features of hypercortisolism.