|
|
| Line 8: |
Line 8: |
| | | | |
| | ==[[Hyperparathyroidism]]== | | ==[[Hyperparathyroidism]]== |
| − | [[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]]
| |
| | | | |
| | | | |