Pituitary Adenoma

Tumors at the pituitary are classified by SIZE and by SECRETIONS. They are treated with medication, surgery, or active surveillance.

Size

A MICROadenoma is less than 1 cm and is often an incidental finding on an MRI of the brain done for other reasons, like workup of a headache. Unless it is secreting active hormone, a small adenoma is asymptomatic and will not cause visual disturbance or headache.

A MACROadenoma is larger than 1 cm and often presents with visual field cut due to compression of the optic chiasm. This produces tunnel vision, with a loss of peripheral vision called bitemporal hemianopsia.

Secretions

Pituitary tumors are also classified by secretions.

A “non-functioning” adenoma does not secrete active hormone. It may actually suppress the production of normal hormones, with TSH, LH, and FSH being most vulnerable. Paradoxically it can result in *mild* elevation of PRL to about 20-100. It is often discovered by visual field loss caused by compression of the optic chiasm causing bitemporal hemianopsia.

“Functioning” pituitary adenomas secrete active hormone. These tumors may secrete any hormone, but PRL, GH, and ACTH are by far the most common.

A PRL secreting tumor mimics the postpartum state in females, with amenorrhea and galactorrhea.  In males it’s even worse: impotence and poor libido! A prolactinoma can be quite large on initial presentation, and the serum PRL may measure in the several hundreds. Fortunately, these are nicely responsive to dopaminergic drugs like bromocriptine and cabergoline, shrinking the tumor dramatically within a few weeks.

A GH secreting tumor causes acromegaly in adults and giantism in children. Acromegaly in adults can occur insidiously, barely noticed by the patient and close family. On questioning the patient may admit enlarged hands and feet such that rings and shoes have been resized. Other stigmata include an enlarged brow, protruding jaw, or enlargement of the cartilaginous nose. One patient noticed that he could floss easier as his teeth separated due to elongation of the jaw! Surgery is needed to remove this tumor.

An ACTH secreting adenoma causes Cushing’s disease, named for Harvey Cushing, the father of neurosurgery. ACTH production in the pituitary stimulates production of cortisol in the adrenal gland. This produces clinical hallmarks of Cushing’s: moon face, buffalo hump, abdominal obesity with striae, wasting of arms and legs, and easy bruising. This, too, is a surgical condition.

Treatment

Non-functioning MICROadenomas: No intervention needed, just periodic MRIs to check for growth, and periodic labs to check endocrine function.

Non-functioning MACROadenoma: Check endocrine labs, especially thyroid and sex hormones which can be diminished in the presence of a tumor. Check visual fields for bitemporal hemianopsia. Transphenoidal adenomectomy surgery can remarkably restore visual fields.

Prolactinoma: Pro-dopamine drugs like bromocriptine or cabergoline shrink the tumor dramatically and help with symptoms in males and females.

GH or ACTH secreting tumors usually need surgical resection to correct the harmful effects of these excess hormones.