Which criteria confirms the diagnosis of acromegaly in a patient?

• A. An elevated serum phosphate concentration
• B. A decreased serum growth hormone releasing factor concentration
• C. No decrease in serum growth hormone concentration 90 minutes after oral glucose administration
• D. An increased serum somatostatin concentration

Answer: (C)

In the diagnosis of acromegaly, the critical criterion is the response of serum growth hormone levels to glucose administration. In a healthy individual, ingestion of glucose leads to a decrease in growth hormone levels due to the inhibitory feedback mechanism of glucose on growth hormone secretion. However, in patients with acromegaly, which is typically caused by a growth hormone-secreting pituitary adenoma, this regulatory mechanism is impaired. As a result, there is no significant decrease in serum growth hormone concentration after oral glucose administration.

This lack of response is a hallmark of acromegaly and is used as a diagnostic criterion, making it a crucial part of the evaluation process for this condition. In contrast, alterations in serum phosphate, growth hormone releasing factor, or somatostatin concentrations may be seen in various clinical settings but are not definitive indicators for confirming acromegaly. Therefore, the absence of a decrease in serum growth hormone concentration after glucose intake is the key factor that supports the diagnosis of acromegaly.