16th September 2024

Investigations

An oral glucose tolerance test (OGTT) is used to confirm the diagnosis. This test involves administering a 75 g oral glucose load, which should suppress GH in normal individuals. IGF-1 levels are used as a screening test and can aid in the diagnosis. IGF-1 is preferred over GH due to its lower variability.

If the blood tests confirm elevated GH levels through the OGTT, an MRI is the preferred imaging method for detecting a pituitary tumour. If no adenoma is identified, cross-sectional imaging of the body should be conducted to identify an ectopic source.

Additionally, pituitary function tests should be performed as acromegaly may affect other pituitary hormones and formal visual testing to assess the extent of the visual field defect. Echocardiogram, sleep studies and isotope bone scans should be considered as acromegaly has many systemic complications.