The extracellular matrix is a three-dimensional network of proteins, 
glycosaminoglycans and other macromolecules. It has a structural support 
function as well as a role in cell adhesion, migration, proliferation, 
differentiation, and survival. The extracellular matrix conveys signals through 
membrane receptors called integrins and plays an important role in pituitary 
physiology and tumorigenesis. There is a differential expression of 
extracellular matrix components and integrins during the pituitary development 
in the embryo and during tumorigenesis in the adult. Different extracellular 
matrix components regulate adrenocorticotropin at the level of the 
proopiomelanocortin gene transcription. The extracellular matrix also controls 
the proliferation of adrenocorticotropin-secreting tumor cells. On the other 
hand, laminin regulates the production of prolactin. Laminin has a dynamic 
pattern of expression during prolactinoma development with lower levels in the 
early pituitary hyperplasia and a strong reduction in fully grown prolactinomas. 
Therefore, the expression of extracellular matrix components plays a role in 
pituitary tumorigenesis. On the other hand, the remodeling of the extracellular 
matrix affects pituitary cell proliferation. Matrix metalloproteinase activity 
is very high in all types of human pituitary adenomas. Matrix metalloproteinase 
secreted by pituitary cells can release growth factors from the extracellular 
matrix that, in turn, control pituitary cell proliferation and hormone 
secretion. In summary, the differential expression of extracellular matrix 
components, integrins and matrix metalloproteinase contributes to the control of 
pituitary hormone production and cell proliferation during tumorigenesis.