Non functioning pituitary adenoma

Clinically non functioning pituitary tumours may be null cell adenomas or have positive staining for other peptides but with no clinically detectable sequelae. Diagnosis requires MRI scanning and assessment of pituitary function.

Baseline investigations - all cases

Full blood count

Useful indicator of general health and underlying disease. 

Normocytic normochromic anaemia and eosinophilia may be seen with glucocorticoid deficiency.

Urea and electrolytes

Useful indicator of general health and underlying disease.

Hyperkalaemia and hyponatraemia may occur in glucocorticoid deficiency.   

Liver function test

Useful indicator of general health and underlying disease.

Also needed as baseline before starting medical treatments.

Bone profile

Useful indicator of general health and underlying disease.

Hypercalcaemia may occur with glucocorticoid deficiency.

Hypercalcaemia is also a useful first line screen for multiple endocrine neoplasia type 1.

Fasting glucose and lipids

Hypopituitary patients have an elevated mortality due to an excess of cardiovascular deaths.

Fasting glucose and lipids are essential for cardiovascular risk modification.

Baseline pituitary function


Prolactin

It is essential to urgently test serum prolactin in a patient with an apparent non-functioning pituitary adenoma, in case this actually represents a macroprolactinoma.

Elevated prolactin also occurs with non-functioning tumours due to loss of dopaminergic inhibition.

Serum prolactin is also affected by many other factors, for example stress, interfering medications (commonly metoclopramide and antipsychotic agents) and PCOS.

Elevated prolactin levels should also prompt the PEG precipitation test to determine whether this is biologically active or the inactive 'macroprolactin'.


9am cortisol

Due to the circadian rhythm of ACTH release, cortisol is best assessed early morning (or on waking in patients with irregular hours, for example shift workers).

Levels above 590nmol/l exclude glucocorticoid deficiency.

Patients with levels below this require formal assessment for ACTH reserve, for example with an insulin stress test or glucagon test.

Ensure patients have stopped sex steroid therapy, for example HRT or the combined oral contraceptive pill for six weeks prior to test.

Estrogen replacement therapy leads to elevation of cortisol binding globulin and hence serum cortisol and so is difficult to interpret. 


Thyroid stimulating hormone, free thyroxine

It is essential to assess levels of both thyroxine and TSH in pituitary patients since a normal TSH level is frequently associated with loss of thyroid function in this patient group.

Levels of both TSH and thyroxine are typically low-normal in hypopituitary patients.


Growth hormone, insulin like growth factor I

Although GH release is pulsatile and so isolated levels are difficult to interpret, recent guidelines recommend that a normal GH and IGF-I taken together form a useful screen for acromegaly. Elevation of either test taken with clinical suspicion mandates a formal GH suppression test with glucose tolerance testing.

Very low IGF-I levels alone are not diagnostic for GH deficiency but are a useful screen mandating a formal GH provocation test, for example insulin stress test or glucagon test.


Luteinising hormone, follicle stimulating hormone

In the presence of pituitary disease, both luteinising hormone and follicle stimulating hormone are typically low, or not elevated in post menopausal women.

This may be due to pituitary failure or a specific consequence of hyperprolactinaemia.


Estrodiol, testosterone, sex hormone binding globulin

These should be assessed early morning, and in the early follicular phase and off the contraceptive pill in women. 

Sex hormone binding globulin is necessary to calculate free androgen index in some cases, for example where the decision to start testosterone replacement is not clear cut.

Further investigations - selected cases only

Paired serum and urine osmolalities

Spot osmalilities may be highly suggestive of diabetes insipidus in a polyuric patient, negating the need for a formal water deprivation test.

Erythrocyte sedimentation rate

Patients presenting with peri sellar masses or unusual features, for example diabetes insipidus should prompt evaluation for possible immune or granulomatous disease.

Auto-antibody screen

Patients presenting with peripituitary masses or unusual features, for example diabetes insipidus, should prompt evaluation for possible immune or granulomatous disease.

Angiotensin converting enzyme

Patients presenting with peripituitary masses or unusual features, for example diabetes insipidus, should prompt evaluation for possible sarcoidosis.

Alfa feto protein, human choriotropic hormone

Patients presenting with peripituitary masses or unusual features, for example diabetes insipidus, should prompt consideration of possible 'non-pituitary' causes, such as germ cell tumours.

Other tumour markers may be tested as indicated, for example the prostate specific antigen.

MRI pituitary

This should be performed in all cases with documented abnormality of pituitary function and urgently if there is visual field loss or optic disc pallor.

PET CT

This may be considered after oncology and MDT review if a germ cell tumour is suspected.

Chest radiograph

All patients presenting with a new pituitary mass should have a CXR performed as an assessment of general health and a simple screen for underlying malignancy.

Peripituitary masses should also prompt evaluation for possible sarcoidosis.

Electrocardiogram

This is usefully performed at presentation as it is required prior to performing an insulin stress test, or considering general anaesthesia.

Visual perimetry and acuity

Formal visual field testing is mandatory if there is clinical or MRI suspicion of chiasmal impingement.

Insulin stress test

This should be performed if GH or ACTH deficiency is suspected but not yet confirmed subject to the usual safety exclusion criteria.

Glucagon test

Glucagon test should be performed if GH or ACTH deficiency is suspected but not yet confirmed and the patient is unable to tolerate an insulin stress test.

Arginine-GHRH testing

When insulin stress testing is unavailable or contraindicated, arginine-GHRH testing is the next best test for assessment of GH reserve. 

Water deprivation test

This should be performed if there is clinical suspicion of diabetes insipidus.