A 15-year-old boy presents with bitemporal hemianopia and spade-like hands. What is the definitive test to confirm the diagnosis?

The definitive test to confirm the diagnosis in a case presenting with bitemporal hemianopia and spade-like hands is an Oral Glucose Tolerance Test (OGTT) combined with growth hormone measurements. In this scenario, the symptoms suggest a growth hormone-secreting pituitary adenoma, which can lead to acromegaly, manifesting as abnormal hand shape, among other features.

During an OGTT, glucose is administered, and the body’s response, particularly the suppression of growth hormone, is measured. In normal physiology, a rise in blood glucose typically leads to a decrease in growth hormone levels. However, in patients with growth hormone-secreting tumors, this suppression does not occur, and growth hormone levels remain elevated even after glucose administration. This characteristic response is crucial for establishing a diagnosis of acromegaly due to a pituitary adenoma.

The other options do not specifically provide the necessary confirmation. Early morning growth hormone measurements may indicate elevated levels but are not definitive without the context of the glucose challenge. The insulin tolerance test assesses growth hormone release but is less commonly used as a diagnostic measure for acromegaly. The short ACTH test evaluates adrenal function rather than growth hormone secretion and is thus not relevant in this context