15th September 2024

Investigations

Basal and dynamic tests are used to assess the function of the hypothalamic-pituitary-hormonal axis. This includes cortisol, prolactin, TSH, Free T4, LH/FSH, testosterone or oestradiol, IGF-1, 9am Cortisol, and ACTH. Baseline posterior pituitary function should also be assessed (covered in another chapter). Dynamic stimulation tests are used to assess hormone under-secretion, including:

• Insulin tolerance test (ITT) for ACTH and GH reserves
• Glucagon test for GH and ACTH reserves
• GHRH and arginine test for GH reserves
• Short synacthen test for ACTH reserves
• CRH stimulation test for adrenal insufficiency
• TRH stimulation test for T3/T4 reserves (for secondary and tertiary hypothyroidism)

For suspected over-secretion in pituitary disorders, use suppression tests such as:

• Oral glucose tolerance test for GH reserves (used for acromegaly)
• Low dose dexamethasone suppression for cortisol levels (used for Cushing’s syndrome)

For other systemic illnesses: serum ACE levels, ferritin, hCG, and alpha-fetoprotein, and perform MRI of the pituitary for optimal imaging.