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Deficient production of anterior pituitary hormones leads to features of hypopituitarism. Impaired production of one or more of the anterior pituitary trophic hormones can result from inherited disorders; more commonly, adult hypopituitarism is acquired and reflects the compressive mass effects of tumors or the consequences of local pituitary or hypothalamic traumatic, autoimmune, inflammatory, or vascular damage. These processes also may impair synthesis or secretion of hypothalamic hormones, with resultant pituitary failure (Table 379-1).
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DEVELOPMENTAL CAUSES OF HYPOPITUITARISM
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Pituitary dysplasia may result in aplastic, hypoplastic, or ectopic pituitary gland development. Because pituitary development follows midline cell migration from the nasopharyngeal Rathke’s pouch, midline craniofacial disorders may be associated with pituitary dysplasia. Acquired pituitary failure in the newborn also can be caused by birth trauma, including cranial hemorrhage, asphyxia, and breech delivery.
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A large number of transcription factors and growth factors are critical for the development of the hypothalamus and pituitary gland and the function of differentiated anterior pituitary cell lineages. Mutations have been described in the HESX1, SOX2, SOX3, LHX3, LHX4, OTX, GLI2, PAX6, BMP4, ARNT2, FGF8, FGFR1, SHH, PROKR2, GPR161, IGSF1, PITX2, and CHD7 genes, among others. Heterozygous loss-of-function or autosomal recessive mutations disrupt hypothalamic and pituitary development at different developmental stages, causing a wide array of phenotypes ranging from severe syndromic midline and other defects to combined pituitary hormone defects or isolated hormone deficiencies. Depending on the gene involved, the pituitary may be hypoplastic, hyperplastic, or ectopic. Midline defects include variable combinations of abnormal development of the eyes, corpus collosum, vertebrae, and genital systems. Pituitary dysfunction ranges from isolated hormone deficiency to combined pituitary hormone deficiency (CPHD) and diabetes insipidus (DI).
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In addition to these syndromic developmental disorders, some mutations affect specific pituitary cell lineages. For example, Pit-1 mutations cause combined growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH) deficiencies. These patients usually present with ...