Abstract
Thanks to experiments on the animal models our knowledges about the embryonal pituitary development have been extended in recent twenty years. It is directed by cascade of signaling molecules and transcription factors produced partly by surroundings tissues, but mainly by the cells of primordial gland's tissues.
The genes for pituitary-specific transcription factors are members of phylogenetically old family of the homeobox genes. Just their distinct, spatial and temporal expression is necessary for shaping of morphologically and functionally competent tissue.
The anterior and intermediate lobes are derived from the oral ectoderm, the posterior lobe from the neuroectoderm of diencephalon. The anterior pituitary development has two phases.
In the first phase is formed the anatomically defined tissue (the morphogenesis of adenohypophysis) - first the thickening of the ectoderm in the ceiling of the oral cavity primordium is forming the pituitary placode, than is formed the Rathke's pouch and finally the tissue is getting the maturated shape and laying on the primordium of the neurohypophysis. This process is governed by transcription factors HESX1, PITX1, PITX2, LHX3 a LHX4.
Their mutations by humans results principle in combined pituitary hormone deficit often accompanied with impaired development of the brain. In the second phase are differentiated individual cell types within the mature anterior pituitary gland.
Besides of plenty extrapituitary signaling molecules this process is directed by two subsequent transcription factors - PROP1 and PIT1 (POU1F1). Their mutations leads also to deficit of several pituitary hormones without any other phenotypic manifestations.
In the Middle Europe the mutations of the PROP1 is the most frequent aetiology of hereditary combined pituitary hormone deficit.