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| | ===[[Congenital Panhypopituitarism]]=== | | ===[[Congenital Panhypopituitarism]]=== |
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| − | Also known as ''Pituitary Dwarfism'', Congenital Panhypopituitarism is defined by failure of differentiation of oesophageal ectoderm from which the pituitary is derived. The pituitary is replaced by a cystic dilatation of ''Rathke's Cleft'' which replaces normal tissue with multilocular cysts- lined with non-secretory cuboidal epithelium.
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| − | [[Image:Pituitary dwarfism.jpg|right|thumb|125px|<small><center>'''Cystic Rathke's Pouch'''. Courtesy of A. Jefferies</center></small>]]
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| − | ''Incidence:''
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| − | *Seen in German Shepherd Dog. Inherited as a simple autosomal recessive trait in affected dogs.
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| − | *Congenital hypoplasia of the pituitary in the cat has also been reported.
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| − | ''Clinical signs:''
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| − | Variable with degree of involvement of the pituitary. Most obvious signs are due to the lack of [[Pituitary Growth Hormone - Anatomy & Physiology|GH]] during the growing phase of the puppy's life:
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| − | *Pups appear normal at birth as the placenta supplies the foetus' need for GH.
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| − | *Retarded growth and proportionate dwarfism.
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| − | *Delayed growth plate closure; long bone physes normally close at 7-12 months but those of a pituitary dwarf will remain open until 3-4 years.
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| − | *Delayed dental eruption.
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| − | *Prognathism; undershot lower jaw as GH needed for mandible length.
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| − | *Pups are quieter, more nervous and perhaps slower to learn.
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| − | *Retention of puppy coat; wooly. Adult coat does not develop and a bilaterally symmetric, non-pruritic alopecia occurs over areas of friction E.g. neck and trunk.
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| − | *Hyperpigmentation with '''comedomes'''.
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| − | *Reproductive signs E.g. failure to cycle, testicular atrophy.
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| − | May also see signs of
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| − | *Secondary hypothyroidism
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| − | *Secondary hypoadrenocorticism
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| − | ''Diagnosis'':
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| − | *Presumptive diagnosis based on signalment and clinical signs.
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| − | *Radiography to detect growth plate closure.
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| − | *'''GH stimulation test'''; Use alpha-2 agonist E.g. ''Xylazine'' which inhibit somatostatin and so induce GH production and release. Normal dogs will have 2-4X increased GH after 20 mins while a pituitary dwarf will show little change in GH upon stimulation.
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| − | *'''Somatomedin Assay'''; Also called '''insulin-like growth factors'''. GH mediates its effects by stimulating the production of IGFs which can be more easily measured. Low levels will be found in pituitary dwarfs.
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| − | *May also need to consider TSH and ACTH stimulation tests.
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| − | ''Treatment:''
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| − | Need to treat early or will remain dwarfs.
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| − | *Sub-cut bovine/human GH can induce the growth of an adult haircoat. <br>Nb. GH is '''diabetogenic''' so overdose will induce Diabetes Mellitus.
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| − | *Progestagens may induce GH production from the mammary gland.
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| − | *May need to replace thyroid hormones and/or glucocorticoids.
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| − | [[Category:Pituitary Gland - Pathology]]
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