metyrapone

[mə-tîrə-pōn′]
n.
  1. An inhibitor of the hydroxylation of adrenocortical steroids administered as a diagnostic aid in determining pituitary gland function.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.