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Chapter 14: Pituitary

Which statement about pituitary microadenomas is true?

(A) By definition, they are less than 1.0 cm in size.

(B) They are best seen on coronal T2 gadolinium-enhanced magnetic resonance scans.

(C) They are rarely found at autopsy in asymptomatic individuals.

(D) Fifteen percent will enlarge to macroadenomas.

(A) The “gold standard” for classifying pituitary adenomas is based on immunohistochemistry and electron microscopy. However, from a surgical standpoint, they can be classified by size and growth characteristics. In the simplest form, adenomas are divided into two groups: microadenomas (<10 mm in diameter) and macroadenomas (≥10 mm in diameter). To further classify macroadenomas, it can be useful to use a system that takes into account grade, degree, and direction of extrasellar extension (stage). Microadenomas of the pituitary are best visualized with a coronal T1 MRI. Eighty to 95% of such studies will show a focal hypointense lesion within an otherwise homogenous adenohypophysis. The excellent sensitivity of unenhanced T1-weighted spin echo (SE) MRI for microadenomas has made it the primary sequence for imaging the pituitary gland. Contrast is reserved for those cases in which there is good clinical or biochemical evidence of a pituitary adenoma with a negative or equivocal plain MRI. In most cases, the best imaging routine is to perform a plain scan followed by a repeat T1-weighted coronal sequence immediately after intravenous injection of contrast (gadolinium). Autopsy studies have repeatedly shown that 20–25% of the general population harbor small pituitary microadenomas. Microadenomas are usually clinically silent and occur in patients without apparent endocrine symptoms. Whereas very few microadenomas will show interval growth, more than one-third of macroadenomas will increase in size.

 

BIBLIOGRAPHY

Atlas S. Magnetic Resonance Imaging of the Brain and Spine, 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009.

Jane J, Thapar K, Laws E. Pituitary tumors. In: Winn HR (ed.), Youmans Neurological Surgery, 6th ed. Philadelphia, PA: W. B. Saunders; 2011:1476–1510.

A 19-year-old woman has had amenorrhea and galactorrhea for 13 months. Her prolactin level is 100 ng/mL (normal 4–23 ng/mL for nonpregnant women). She brought a recent magnetic resonance image (MRI) with her (see Fig. 14-1). After other causes of hyperprolactinemia have been ruled out, she should

 

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FIGURE 14-1. Coronal magnetic resonance scan (T1 with contrast).

 

(A) Begin medical therapy with dopamine agonists

(B) Begin medical therapy with oral contraceptives

(C) Begin calcium supplementation

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