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Created page with "thumb|right|100px|Parathyroid adenoma. Image courtesy of Biomed Archive. ===Primary=== * Primary hyperparathyroidism is caused by glandular hyperp..."
[[Image:parathyroidadeoma.jpg|thumb|right|100px|Parathyroid adenoma. Image courtesy of Biomed Archive.]]
===Primary===
* Primary hyperparathyroidism is caused by glandular hyperplasia or neoplasia. [[Image:parathyroidhyperplasia.jpg|thumb|right|100px|Parathyroid hyperplasia. Image courtesy of Biomed Archive.]]
* Rare.
===Secondary===
* Secondary hyperparathyroidism causes [[Bones Metabolic - Pathology#Hyperparathyroidism|fibrous osteodystrophy or "rubber jaw"]].
* In secondary hyperparathyroidism, the gland is overactive due to another condition coexisting in the body, rather than a primary parathyroid gland defect.
* There are two common forms of secondary hyperparathyroisism:
*# [[Parathyroid Glands - Pathology#Nutritional Hyperparathyroidism|'''Nutritional Hyperparathyroidism''']]
*#* This includes [[Parathyroid Glands - Pathology#Metabolic Bone Disease|Metabolic Bone Disease]].
*# [[Parathyroid Glands - Pathology#Renal Hyperparathyroidism|'''Renal Hyperparathyroidism''']]
* Both forms result in increased osteoclastic resorption of bone and deposition of fibro-osteoid matrix that fails to mineralise.
** Flat bones of the skull swell.
** Fibrous tissue is seen around the tooth roots.
** Bone softens in adult animals.
*** This is what gives rise to the term "rubber jaw".
*** Long bones become soft with thin cortices.
**** These fracture easily.
====Nutritional Hyperparathyroidism====
[[Image:secondaryhyperparathyroidism.jpg|thumb|right|100px|Secondary hyperparathyroidism - "rubber jaw". Image courtesy of Biomed Archive.]]
* Nutritional hyperparathyroidism is also known as nutritional osteodystrophy.
* This occurs most commonly in:
** Young, fast-growing animals
** Animals with a poor diet, for example:
*** Swine fed unsupplemented cereal grain
*** Dogs and cats fed all-meat diets
*** Horses fed bran
**** In this case, nutritional hyperparathyroidism is known as "bran disease".
=====Pathogenesis=====
* Pathogenesis follows low calcium/high phosphate diets.
** These lead to decreased serum calcium levels, stimulating [[Parathyroid Glands - Pathology#Hormonal Control|PTH]] release.
** The increase in PTH gives an increase in bone resorption, causing pathology.
=====Pathology=====
* '''Gross'''
** Severe cases may show:
*** Maxillary and mandibular swelling
*** [[:Category:Teeth - Anatomy & Physiology|Teeth]] lost or buried in soft tissue
*** Nasal and frontal bone enlargement, leading to dyspnoea
*** Long bone fracture
*** Detatchment tendons and ligaments
** Early or less severe cases are characterised by shifting lameness and ill thrift.
* '''Histological'''
** Osteoclastic resorption
** Fibrous replacement
=====Metabolic Bone Disease=====
* Metabolic bone disease affects lizards in captivity, particularly young green iguanas
* The condition is caused by:
** Dietary deficiency of calcium and vitamin D
*** For example, due to poor lighting (which diminishes viatmin D production).
** Dietary excess of phosphorus
** Certain toxicities
** Diseases of the kidneys, [[Liver - Anatomy & Physiology|liver]] or parathyroid
*** This aetiology is rare
* Clinical signs include:
** Lethargy
** Inability to support weight
** Rounded skull
** Spontaneous fractures
** Adult animals also show signs of [[Parathyroid Glands - Pathology#Hypocalcaemia|hypocalcaemia]]
* The skeleton shows reduced density on radiography.
====Renal Hyperparathyroidism====
* Renal Hyerparathyroidism is mostly seen in the dog as an expression of chronic renal disease.
=====Pathogenesis=====
[[Image:renalhyperparathyroidism.jpg|thumb|right|100px|Parathyroid hyperplasia in renal hyperparathyroidism. Image courtesy of Biomed Archive.]]
# Chronic renal disease results in reduced glomerular filtration.
# As glomerular filtration is reduced, phosphate is retained. Chronic renal failure also causes inadequate vitamin D production in the kidneys.
# Hyperphosphataemia develops due to phosphate retention.
#* Hypocalcaemia also occurs, as high levels of phosphate depress calcium levels.
# PTH is released in an attempt to maintain the correct blood calcium:phosphorous ratio. This can have several effects:
#* Parathyroid hyperplasia
#** I.e. '''renal secondary hyperparathyroidism'''.
#* Soft tissue mineralisation
#** Particularly seen in dogs
#** Calcium is commonly deposited in the subpleural connective tissue of the intercostal spaces.
#** Calcification also occurs in other sites, e.g. [[Monogastric Stomach - Anatomy & Physiology|stomach]] wall, lungs, kidneys.
#* Increased bone resorption
#** This causes fibrous osteodystrophy, or "rubber jaw".
=====Pathology=====
[[Image:Renal_osteodystrophy.jpg|thumb|right|100px|"Rubber jaw" in renal osteodystrophy. Image courtesy of Biomed Archive.]]
* Pathology seen in renal hyperparathyroidism is very similar to that seen in nutritional hyperparathyroidism.
* '''Gross'''
** The major gross presentation is a fibrous osetodystrophy, or rubber jaw.
*** The maxillae and mandible appear swollen.
*** Radiographically, bone shows reduced density, and [[:Category:Teeth - Anatomy & Physiology|teeth]] hence appear embedded in soft tissue.
*** However, only a few cases of chronic renal disease show such severe bone lesions.
** Other lesions may also be seen.
*** Intercostal muscles may be calcified.
*** Bone marrow lesions may cause anaemia.
*** The lung may show oedema, and have calcified alveolar walls.
* '''Histological'''
** Osteoclastic resorption
** Fibrous replacement
[[Category:Parathyroid Glands - Pathology]]
===Primary===
* Primary hyperparathyroidism is caused by glandular hyperplasia or neoplasia. [[Image:parathyroidhyperplasia.jpg|thumb|right|100px|Parathyroid hyperplasia. Image courtesy of Biomed Archive.]]
* Rare.
===Secondary===
* Secondary hyperparathyroidism causes [[Bones Metabolic - Pathology#Hyperparathyroidism|fibrous osteodystrophy or "rubber jaw"]].
* In secondary hyperparathyroidism, the gland is overactive due to another condition coexisting in the body, rather than a primary parathyroid gland defect.
* There are two common forms of secondary hyperparathyroisism:
*# [[Parathyroid Glands - Pathology#Nutritional Hyperparathyroidism|'''Nutritional Hyperparathyroidism''']]
*#* This includes [[Parathyroid Glands - Pathology#Metabolic Bone Disease|Metabolic Bone Disease]].
*# [[Parathyroid Glands - Pathology#Renal Hyperparathyroidism|'''Renal Hyperparathyroidism''']]
* Both forms result in increased osteoclastic resorption of bone and deposition of fibro-osteoid matrix that fails to mineralise.
** Flat bones of the skull swell.
** Fibrous tissue is seen around the tooth roots.
** Bone softens in adult animals.
*** This is what gives rise to the term "rubber jaw".
*** Long bones become soft with thin cortices.
**** These fracture easily.
====Nutritional Hyperparathyroidism====
[[Image:secondaryhyperparathyroidism.jpg|thumb|right|100px|Secondary hyperparathyroidism - "rubber jaw". Image courtesy of Biomed Archive.]]
* Nutritional hyperparathyroidism is also known as nutritional osteodystrophy.
* This occurs most commonly in:
** Young, fast-growing animals
** Animals with a poor diet, for example:
*** Swine fed unsupplemented cereal grain
*** Dogs and cats fed all-meat diets
*** Horses fed bran
**** In this case, nutritional hyperparathyroidism is known as "bran disease".
=====Pathogenesis=====
* Pathogenesis follows low calcium/high phosphate diets.
** These lead to decreased serum calcium levels, stimulating [[Parathyroid Glands - Pathology#Hormonal Control|PTH]] release.
** The increase in PTH gives an increase in bone resorption, causing pathology.
=====Pathology=====
* '''Gross'''
** Severe cases may show:
*** Maxillary and mandibular swelling
*** [[:Category:Teeth - Anatomy & Physiology|Teeth]] lost or buried in soft tissue
*** Nasal and frontal bone enlargement, leading to dyspnoea
*** Long bone fracture
*** Detatchment tendons and ligaments
** Early or less severe cases are characterised by shifting lameness and ill thrift.
* '''Histological'''
** Osteoclastic resorption
** Fibrous replacement
=====Metabolic Bone Disease=====
* Metabolic bone disease affects lizards in captivity, particularly young green iguanas
* The condition is caused by:
** Dietary deficiency of calcium and vitamin D
*** For example, due to poor lighting (which diminishes viatmin D production).
** Dietary excess of phosphorus
** Certain toxicities
** Diseases of the kidneys, [[Liver - Anatomy & Physiology|liver]] or parathyroid
*** This aetiology is rare
* Clinical signs include:
** Lethargy
** Inability to support weight
** Rounded skull
** Spontaneous fractures
** Adult animals also show signs of [[Parathyroid Glands - Pathology#Hypocalcaemia|hypocalcaemia]]
* The skeleton shows reduced density on radiography.
====Renal Hyperparathyroidism====
* Renal Hyerparathyroidism is mostly seen in the dog as an expression of chronic renal disease.
=====Pathogenesis=====
[[Image:renalhyperparathyroidism.jpg|thumb|right|100px|Parathyroid hyperplasia in renal hyperparathyroidism. Image courtesy of Biomed Archive.]]
# Chronic renal disease results in reduced glomerular filtration.
# As glomerular filtration is reduced, phosphate is retained. Chronic renal failure also causes inadequate vitamin D production in the kidneys.
# Hyperphosphataemia develops due to phosphate retention.
#* Hypocalcaemia also occurs, as high levels of phosphate depress calcium levels.
# PTH is released in an attempt to maintain the correct blood calcium:phosphorous ratio. This can have several effects:
#* Parathyroid hyperplasia
#** I.e. '''renal secondary hyperparathyroidism'''.
#* Soft tissue mineralisation
#** Particularly seen in dogs
#** Calcium is commonly deposited in the subpleural connective tissue of the intercostal spaces.
#** Calcification also occurs in other sites, e.g. [[Monogastric Stomach - Anatomy & Physiology|stomach]] wall, lungs, kidneys.
#* Increased bone resorption
#** This causes fibrous osteodystrophy, or "rubber jaw".
=====Pathology=====
[[Image:Renal_osteodystrophy.jpg|thumb|right|100px|"Rubber jaw" in renal osteodystrophy. Image courtesy of Biomed Archive.]]
* Pathology seen in renal hyperparathyroidism is very similar to that seen in nutritional hyperparathyroidism.
* '''Gross'''
** The major gross presentation is a fibrous osetodystrophy, or rubber jaw.
*** The maxillae and mandible appear swollen.
*** Radiographically, bone shows reduced density, and [[:Category:Teeth - Anatomy & Physiology|teeth]] hence appear embedded in soft tissue.
*** However, only a few cases of chronic renal disease show such severe bone lesions.
** Other lesions may also be seen.
*** Intercostal muscles may be calcified.
*** Bone marrow lesions may cause anaemia.
*** The lung may show oedema, and have calcified alveolar walls.
* '''Histological'''
** Osteoclastic resorption
** Fibrous replacement
[[Category:Parathyroid Glands - Pathology]]