Incidence of pituitary tumors
8-10% of all intracranial tumors
Pituitary adenoma origin
From anterior lobe (adenohypophysis)
Microadenoma vs. macroadenoma
Micro: < 10mm
Macro: >10mm
Pituitary adenoma spread and consequences
Local invasion inferiorly through floor of sella (CSF rhinorrhea)
Superiorly to suprasellar cisterns (compression of optic chiasm, hypothalamus, 3rd ventricle)
Laterally to cavernous sinus (CN disturbance)
Lateral microadenomas are more likely to produce which hormones?
Prolactin and GH
Central microadenomas are more likely to produce which hormone?
ACTH
Effects of prolactin
Breast growth and promotion of lactation; important in spermatogenesis
How is prolactin secretion regulated?
Dopamine blocks prolactin secretion (UNLIKE ALL OTHER PITUITARY HORMONES)
Characteristic presentation of prolactinomas
Young females with amenorrhea and galactorrhea; males with impotence
Prolactin level suggestive of pituitary adenoma
>2000 ng/mL (nl 70-550)
Other pituitary adenomas associated with hyperprolactinemia
GH and null cell can cause hyperprolactinemia 2/2 mass effect blocking DA secretion
Consequences of ACTH adenoma
ACTH stimulates adrenal cortex to secrete cortisol = CUSHING'S DISEASE
Null cell adenoma histology
Chromophobic (no cytoplasmic granules) + accumulation of mitochondria (then called 'oncocytomas')
Null cell adenoma presentation
Aggressive and grow quickly = visual disturbances
Hormonally silent
Factors affecting presentation of pituitary adenomas
Size of tumor + endocrine fxn of secreted hormones
Visual field deficits a/w pituitary adenoma
Compression of optic chiasm -> bitemporal hemianopsia
Compression of optic tract -> homonymous hemianopsia
Compression of posterior chiasm -> bilateral central scotomas
Extraocular deficits a/w pituitary adenomas
CN3, 4, 6 palsies
CN5 damage 2/2 cavernous sinus invasion causes facial pain
Sxs of hypopituitarism
Pre-pubertal: retards development of 2ndary sex characteristics
Post-pubertal: fatigue, muscle weakness, anorexia --> episodic confusion/drowsiness (severe) can be precipitated by stressful events
Sxs of pituitary apoplexy
Spontaneous hemorrhage into pituitary tumor = sudden severe HA, transient LOC + extraocular muscle paralysis (looks like SAH + EOM involvement)
What do GH-secreting tumors cause?
Kids - gigantism
Adults (30-40) - acromegaly (enlarged hands/feet, coarse/greasy skin, sweat profusely, HTN, cardiac hypertrophy, diabetes)
Cushing's disease
ACTH-producing pituitary adenoma (80% microadenomas)
Cushing's disease mortality
50% at 5 years
Cushing's disease sxs
Obesity, thin skin, striae, fat redistribution (moon face, buffalo hump), easy bruising, acne, facial hair, weakness/muscle atrophy, osteoporosis, glucose intolerance
Causes of Cushing's syndrome
90% of cases 2/2 Cushing's disease (ACTH-producing pituitary adenoma)
OTHER: adrenal adenoma/carcinoma or ectopic ACTH (small cell lung CA)
Nelson-Salassa syndrome
ACTH-producing pituitary adenoma in pt w/ bilateral adrenalectomy -> no negative feedback -> accelerated growth of existing adenoma (usually macroadenoma)
Cutaneous findings of Nelson-Salassa syndrome
Hyperpigmentation 2/2 beta-MSH production (ACTH breakdown product)
How is GH-secreting tumor diagnosed?
Glucose suppression test - measure GH following glucose bolus (should suppress normally)
IGF-1 levels - indicator of GH activity
Other: measure GHRH or TRH
How is Cushing's disease diagnosed?
1. Hypercortisolemia on 24 hr urine cortisol
2. Dexamethasone suppression test (high-dose will suppress pituitary adenoma but NOT ectopic or adrenal ACTH source)
3. Administer CRH and measure differential ACTH level in periphery/pertrosal sinus
Scan of choice for pituitary adenomas?
High resolution CT/MRI with contrast
Appearance of pituitary micro vs. macroadenoma on CT?
Micro: hypodense, upward bulging, deviation of pituitary stalk, thinning of sella
Macro: contrast-enhancing lesion in sella, best seen on coronal section
