Pituitary Macroadenoma

Approach to Pituitary Macroadenoma

• Pituitary adenomas are classified based on size and function:
• Macroadenoma vs Microadenoma
• Functioning vs non-functioning
• Causes problems by:
• Hypersecretion: Most common are gonadotroph secreting adenomas, but they are hardest to recognize as they secrete inefficiently and the effects are not easily noticed; prolactin (PRL), responsible for amenorrhea-galactorrhea in women and decreased libido in men; growth hormone (GH), responsible for acromegaly; adrenocorticotropic hormone (ACTH), responsible for Cushing's disease; thyroid-stinulating hormone (TSH), responsible for hyperthyroidism. 
• Depressed secretion of hormones: Hypopituitarism, in the order of: GH, LH/FSH, TSH, ACTH, PRL (aka Go Look For The Adenoma Please)
• Mechanical compression
• Expansion of dura causes headaches
• Superior invasion: affects optic chiasm and causes bitemporal hemianopsia
• Inferior invasion: Through cribriform plate into sphenoid sinus causing CSF rhinorrea and risk of meningitis
• Lateral invasion: Cavernous sinus/internal carotid artery and cranial nerves 3, 4, 6, 5 (V1/V2)

• Investigation:
• Mechanical compression/extension: 
• Assessed by MRI
• Also can do visual field testing
• Hormone secretion:
• GH: is normally secreted in a diurnal pattern and is suppressed by glucose load. Tested by doing an oral glucose tolerance test. Also can test IGF-1 which does not change hour by hour and reflects integrated GH secretion during the previous 24hrs. Also can test response to OGTT, as patients have insulin resistance.
• TSH/T3/T4
• Cortisol: Screening tests: 24 UFC, late night salivary cortisol, 1mg Dex suppression test
• Prolactin: Prolactin level
• Hormone suppression:
• GH, LH/FSH/Testosterone, TSH, AM cortisol, prolactin
• Comorbidities:
• If patient found to have GH secreting adenoma should look for visceral organ effects:
• Colonoscopy to look for polyps/colon ca
• ECHO to look for cardiomyopathy
• BP to look for HTN
• Fasting BG, OGTT to screen for diabetes
• Screen for obstructive sleep apnea

• Management:
• Surgical indications:
• A visual field deficit due to the lesion or other visual abN
• Adenoma abutting the optic chiasm on MRI
• Pituitary apoplexy with visual disturbance
• Hypersecreting tumour other than prolactinoma
• Specific situations
• GH secreting adenoma: First line is surgery. Medical therapies include somatostatin analogues (octreotide/lanreotide) and dopamine agonist (cabergoline) and GH receptor antagonists (Pegvisomant). Can also use radiation (fractionated or by Gamma knife).
• ACTH secreting tumour: primary therapy is surgery
• Prolactinoma: Can use medical therapy with DA agonist.
• Micro-incidentalomas
• Follow-up MRI in 1 yr and then Q1-2 y thereafter
• If grows significantly (in proportion to original size) then consider surgery
• Macro-incidentalomas
• Follow up MRI in 6 months then Q1yr
• Evaluate for hypopituitarism and evaluate the visual fields
• If there is tumour growth, VF abN or hypopit consider surgery

See the Endocrine Society Practice Guidelines for an Approach to Pituitary Incidentaloma