Clinically nonfunctioning pituitary adenomas.

Clinically nonfunctioning pituitary adenomas do not produce a readily recognizable clinical syndrome attributable to hormonal secretion. Any kind of pituitary adenoma may be clinically nonfunctioning, but gonadotroph and thyrotroph adenomas are more likely to be nonfunctioning, lactotroph adenomas less likely, and somatotroph and corticotroph adenomas least likely. Clinically nonfunctioning adenomas usually come to medical attention when they become so large that they cause neurologic symptoms, especially visual impairment. Although they are difficult to recognize clinically, they can be identified in vivo by measurement of basal and TRH-stimulated concentrations of follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone, and their subunits. They can also be recognized in vitro by secretion in culture, immunospecific staining, and probing for mRNAs. Primary treatment is usually transsphenoidal surgery, and adjunctive treatment may include supervoltage radiation, and occasionally, pharmacologic agents.