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Pharyngeal pituitary: development, malformation, and tumorigenesis
1Institute of Neuropathology, Medizinische Hochschule Hannover, Germany. hori.akira@mh-hannover.de
Insights
The pharyngeal pituitary (PhP) develops later than the sellar pituitary (SP) and is present in all individuals, even anencephalic ones. Its development and malformations offer insights into pituitary tumors and brain development.
Area of Science:
- Developmental biology
- Endocrinology
- Neuroscience
Background:
- The pharyngeal pituitary (PhP) is a distinct pituitary structure whose developmental trajectory and functional significance remain incompletely understood.
- Previous research has primarily focused on the sellar pituitary (SP), leaving the PhP's embryogenesis and potential roles less explored.
Observation:
- Morphological and immunohistochemical analyses revealed that PhP begins hormone production at 17-18 weeks of gestation, significantly later than SP.
- A rare craniopharyngeal pituitary (CPhP) remnant was observed in one fetus, and ectopic pituitary adenomas often appear in locations corresponding to PhP.
- Systemic examination of fetuses with cranioneural malformations identified novel PhP malformations, including agenesis, fragmentation, and pharyngosellar pituitary formations.
Findings:
- PhP is consistently present across all examined fetuses, including anencephalic individuals, challenging previous assumptions about SP agenesis in anencephaly.
- Hormone production in malformed PhP tends to be delayed, suggesting developmental vulnerability.
- The consistent location of ectopic pituitary adenomas strongly implicates PhP as a potential origin, though CPhP cannot be entirely ruled out.
Implications:
- This study provides the first comprehensive description of PhP development and its associated malformations.
- Findings suggest PhP plays a crucial role in pituitary development and may be the origin of certain ectopic pituitary adenomas.
- The presence of PhP in anencephalic fetuses necessitates a re-evaluation of pituitary development in severe congenital brain malformations.
Abstract:
The development of the pharyngeal pituitary (PhP) in the fetal period was morphologically and, for the first time, immunohistochemically examined. PhP, found in every individual, begins its hormone production at the 17-18th week of gestation, that is, 4-8 weeks later than that of sellar pituitary (SP). Only 1 of 25 examined fetuses without any stigmata of developmental anomalies showed a residual pituitary fragment in the craniopharyngeal canal (craniopharyngeal pituitary, CPhP). An adult case of a rare clivus pituitary adenoma that we examined is demonstrated in discussing its relationship to PhP. Extracranial ectopic pituitary adenomas in the literature describe an exclusively sphenoid sinus/nasopharyngeal/clivus location of the tumor. Their location corresponded exactly with that of PhP, so that the origin of the tumors can be reasonably speculated as PhP, although another origin, e.g., CPhP, can not be excluded. A variety of malformations of PhP, although very rare, have been described for the fist time during the systemic examination of 16 fetuses with different cranioneural malformations, such as agenesis, unseparated PhP from SP (pharyngosellar pituitary), fragmentation, and residual pituitary tissue in the open craniopharyngeal canal. However, developmental anomaly of PhP was not specifically associated with cranioneural malformations except in cases of chromosomal aberrations. The hormone production in PhP in malformation cases tended to be retarded. Absence of SP was recorded in 50% of anencephalics in the literature; however, PhP was identified in all anencephalics in our series, independent of the existence of SP. This supports the opinion that agenesis of SP in anencephalics seems to be false information.