Pit-1 and hypopituitarism.

The story of Pit-1 and hypopituitarism in humans provides an excellent example of pleiotrophism or multiple phenotypic effects resulting from a single genetic alteration. It shows how defects in this single gene cause the absence o f several pituitary hormones. Three recent articles reviewed here provide examples of different mutations in this homeobox gene encoding a transcriptional activation protein that is vital to the embryologic development, survival, and differentiated function of somatotropes, lactotropes, and thyrotropes.