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| − | {{toplink
| + | #REDIRECT[[:Category:Parathyroid Glands - Pathology]] |
| − | |backcolour = FAFAD2
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| − | |linkpage =Endocrine System - Pathology
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| − | |linktext =Endocrine System
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| − | |maplink = Endocrine System (Content Map) - Pathology
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| − | |pagetype =Pathology
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| − | }}
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| − | <br>
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| − | ==Anatomy and Physiology==
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| − | Anatomy and Physiology of the Parathyroid glands can be found [[Endocrine System - Parathyroid Glands - Anatomy & Physiology|here]].
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| − | ==Hypercalcaemia==
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| − | * Hypercalcaemia should not be ignored in an unwell animal.
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| − | ** The consequences of hypercalcaemia may be serious: prolonged untreated hypercalcaemia can lead to irreversible damage to many organs, particularly the kidneys.
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| − | ** There are multiple causes of hypercalcaemia, but if it is caught early a specific diagnosis and treatment are often possible.
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| − | * The clinical signs of hypercalcaemia are often vague.
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| − | ** Signs commonly include:
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| − | *** PU/PD
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| − | *** Anorexia
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| − | *** Dehydration
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| − | *** Weakness or lethargy
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| − | *** [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|Vomiting]]
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| − | *** Prerenal azotaemia
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| − | ** More uncommonly, hypercalcaemia may present with:
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| − | *** Constipation
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| − | *** Cardiac arrhythmia
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| − | *** Seizures or twitching
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| − | *** [[Kidney Renal Failure - Pathology#Acute|Acute renal failure]]
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| − | *** Death
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| − | * Causes of hypercalcaemia may be:
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| − | *# Nonpathologic
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| − | *#* This may be due to:
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| − | *#** Age - young animals have naturally higher calcium levels.
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| − | *#** Lab error
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| − | *#** Lipaemia
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| − | *#* It is important to establish whether hypercalcaemia is true before persuing further diagnosis and treatment.
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| − | *# Transient...
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| − | *#* ...hypoadrenocorticism
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| − | *#* ...haemoconcentration
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| − | *#* ...hyperproteinaemia
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| − | *# Pathological
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| − | *#* Malignancy
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| − | *#* Lymphoma
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| − | *#* [[Parathyroid Glands - Pathology#Apocrine Gland Adenocarcinoma|Anal sac adenocarcinoma]]
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| − | *#* [[Kidney Renal Failure - Pathology|Renal failure]]
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| − | *#* [[Bones Metabolic - Pathology#Hypervitaminosis D|Hypervitaminosis D]]
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| − | *#* Granulomatous disease
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| − | *#** E.g fungal infections
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| − | *#* [[Parathyroid Glands - Pathology#Primary|Primary hyperparathyroidism]]
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| − | *#* Skeletal lesions
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| − | ==Hypocalcaemia==
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| − | * Hypocalcaemia is a relatively common finding in
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| − | ** Small animals
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| − | *** Most often associated with decreased albumin concentrations.
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| − | *** Usually clinically insignificant.
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| − | ** Farm animals
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| − | *** For example, dairy cows following parturition.
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| − | **** More clinically significant.
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| − | * Clinical signs may not always be present (i.e. clinically insignificant).
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| − | ** Clinical signs are most often seen in associated with lactation or post-operative causes.
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| − | ** When they seen, signs commonly include:
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| − | *** Facial rubbing
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| − | *** Muscle tremors or cramps
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| − | *** Stiff gait
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| − | *** Behavioural changes
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| − | ** The following are seen less commonly:
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| − | *** Panting
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| − | *** Pyrexia
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| − | *** Lethargy
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| − | *** Anorexia
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| − | *** Tachycardia or ECG abnormalities
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| − | *** Hypotension
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| − | *** Death
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| − | * Some causes of hypocalcaemia are also more common than others.
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| − | ** Common causes are:
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| − | *** Chronic renal failure
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| − | *** Hypoalbuminaemia
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| − | *** Eclampsia
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| − | *** Acute pancreatitis
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| − | *** Iatrogenic
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| − | *** Post thyroidectomy
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| − | *** Post parathyroidectomy
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| − | *** Blood transfusion
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| − | ** More uncommonly:
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| − | *** Lab error
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| − | *** Ethylene glycol toxicity
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| − | *** NaHCO<sub>3</sub> administration
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| − | *** Hypovitaminosis D
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| − | *** Hypomagnesaemia
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| − | *** Intestinal malabsorption
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| − | *** Primary hypoparathyroidism
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| − | ==Hyperparathyroidism==
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| − | [[Image:parathyroidadeoma.jpg|thumb|right|100px|Parathyroid adenoma. Image courtesy of Biomed Archive.]]
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| − | ===Primary===
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| − | * Primary hyperparathyroidism is caused by glandular hyperplasia or neoplasia. [[Image:parathyroidhyperplasia.jpg|thumb|right|100px|Parathyroid hyperplasia. Image courtesy of Biomed Archive.]]
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| − | * Rare.
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| − | ===Secondary===
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| − | * Secondary hyperparathyroidism causes [[Bones Metabolic - Pathology#Hyperparathyroidism|fibrous osteodystrophy or "rubber jaw"]].
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| − | * In secondary hyperparathyroidism, the gland is overactive due to another condition coexisting in the body, rather than a primary parathyroid gland defect.
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| − | * There are two common forms of secondary hyperparathyroisism:
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| − | *# [[Parathyroid Glands - Pathology#Nutritional Hyperparathyroidism|'''Nutritional Hyperparathyroidism''']]
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| − | *#* This includes [[Parathyroid Glands - Pathology#Metabolic Bone Disease|Metabolic Bone Disease]].
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| − | *# [[Parathyroid Glands - Pathology#Renal Hyperparathyroidism|'''Renal Hyperparathyroidism''']]
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| − | * Both forms result in increased osteoclastic resorption of bone and deposition of fibro-osteoid matrix that fails to mineralise.
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| − | ** Flat bones of the skull swell.
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| − | ** Fibrous tissue is seen around the tooth roots.
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| − | ** Bone softens in adult animals.
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| − | *** This is what gives rise to the term "rubber jaw".
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| − | *** Long bones become soft with thin cortices.
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| − | **** These fracture easily.
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| − | ====Nutritional Hyperparathyroidism====
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| − | [[Image:secondaryhyperparathyroidism.jpg|thumb|right|100px|Secondary hyperparathyroidism - "rubber jaw". Image courtesy of Biomed Archive.]]
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| − | * Nutritional hyperparathyroidism is also known as nutritional osteodystrophy.
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| − | * This occurs most commonly in:
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| − | ** Young, fast-growing animals
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| − | ** Animals with a poor diet, for example:
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| − | *** Swine fed unsupplemented cereal grain
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| − | *** Dogs and cats fed all-meat diets
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| − | *** Horses fed bran
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| − | **** In this case, nutritional hyperparathyroidism is known as "bran disease".
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| − | =====Pathogenesis=====
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| − | * Pathogenesis follows low calcium/high phosphate diets.
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| − | ** These lead to decreased serum calcium levels, stimulating [[Parathyroid Glands - Pathology#Hormonal Control|PTH]] release.
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| − | ** The increase in PTH gives an increase in bone resorption, causing pathology.
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| − | =====Pathology=====
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| − | * '''Gross'''
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| − | ** Severe cases may show:
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| − | *** Maxillary and mandibular swelling
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| − | *** [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|Teeth]] lost or buried in soft tissue
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| − | *** Nasal and frontal bone enlargement, leading to dyspnoea
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| − | *** Long bone fracture
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| − | *** Detatchment tendons and ligaments
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| − | ** Early or less severe cases are characterised by shifting lameness and ill thrift.
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| − | * '''Histological'''
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| − | ** Osteoclastic resorption
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| − | ** Fibrous replacement
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| − | =====Metabolic Bone Disease=====
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| − | * Metabolic bone disease affects lizards in captivity, particularly young green iguanas
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| − | * The condition is caused by:
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| − | ** Dietary deficiency of calcium and vitamin D
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| − | *** For example, due to poor lighting (which diminishes viatmin D production).
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| − | ** Dietary excess of phosphorus
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| − | ** Certain toxicities
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| − | ** Diseases of the kidneys, [[Liver - Anatomy & Physiology|liver]] or parathyroid
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| − | *** This aetiology is rare
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| − | * Clinical signs include:
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| − | ** Lethargy
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| − | ** Inability to support weight
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| − | ** Rounded skull
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| − | ** Spontaneous fractures
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| − | ** Adult animals also show signs of [[Parathyroid Glands - Pathology#Hypocalcaemia|hypocalcaemia]]
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| − | * The skeleton shows reduced density on radiography.
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| − | ====Renal Hyperparathyroidism====
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| − | * Renal Hyerparathyroidism is mostly seen in the dog as an expression of chronic renal disease.
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| − | =====Pathogenesis=====
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| − | [[Image:renalhyperparathyroidism.jpg|thumb|right|100px|Parathyroid hyperplasia in renal hyperparathyroidism. Image courtesy of Biomed Archive.]]
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| − | # Chronic renal disease results in reduced glomerular filtration.
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| − | # As glomerular filtration is reduced, phosphate is retained. Chronic renal failure also causes inadequate vitamin D production in the kidneys.
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| − | # Hyperphosphataemia develops due to phosphate retention.
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| − | #* Hypocalcaemia also occurs, as high levels of phosphate depress calcium levels.
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| − | # PTH is released in an attempt to maintain the correct blood calcium:phosphorous ratio. This can have several effects:
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| − | #* Parathyroid hyperplasia
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| − | #** I.e. '''renal secondary hyperparathyroidism'''.
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| − | #* Soft tissue mineralisation
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| − | #** Particularly seen in dogs
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| − | #** Calcium is commonly deposited in the subpleural connective tissue of the intercostal spaces.
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| − | #** Calcification also occurs in other sites, e.g. [[Forestomach - Anatomy & Physiology|stomach]] wall, lungs, kidneys.
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| − | #* Increased bone resorption
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| − | #** This causes fibrous osteodystrophy, or "rubber jaw".
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| − | =====Pathology=====
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| − | [[Image:Renal_osteodystrophy.jpg|thumb|right|100px|"Rubber jaw" in renal osteodystrophy. Image courtesy of Biomed Archive.]]
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| − | * Pathology seen in renal hyperparathyroidism is very similar to that seen in nutritional hyperparathyroidism.
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| − | * '''Gross'''
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| − | ** The major gross presentation is a fibrous osetodystrophy, or rubber jaw.
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| − | *** The maxillae and mandible appear swollen.
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| − | *** Radiographically, bone shows reduced density, and [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]] hence appear embedded in soft tissue.
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| − | *** However, only a few cases of chronic renal disease show such severe bone lesions.
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| − | ** Other lesions may also be seen.
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| − | *** Intercostal muscles may be calcified.
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| − | *** Bone marrow lesions may cause anaemia.
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| − | *** The lung may show oedema, and have calcified alveolar walls.
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| − | * '''Histological'''
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| − | ** Osteoclastic resorption
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| − | ** Fibrous replacement
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| − | ==Pseudo-Hyperparathyroidism==
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| − | * Non-endocrine tumours may be capable of secreting hormones, or hormone-like factors.
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| − | ** A parathormone-like substance may be secreted in such a manner.
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| − | ===Apocrine Gland Adenocarcinoma===
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| − | * Malignant tumours of the anal sac apocrine glands can produce PTH-related peptide (PTHrp).
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| − | ** This induces a pseudo-hyperparathyroidism and hypercalcaemia.
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| − | ===[[Lymph Nodes - Pathology#Neoplasia|Lymphosarcoma]]===
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| − | * 10 to 40% of cases in dogs may cause a pseudo-hyperparathyroidism.
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| − | ===Other Carcinomas===
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| − | Some other carcinomas may also be capable of causing pseudo-hyperparathyroidism.
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| − | ==Hypoparathyroidism==
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| − | * Hypoparathyroidism may result from primary gland hypofunction.
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| − | ** Gland hypofunction occurs due to:
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| − | **# Destruction of secretory cells by a disease process.
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| − | **#* For example, this may be immune mediated, or another inflammatory cause.
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| − | **# A biochemical defect in synthetic pathway of the hormone.
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| − | **#* These are usually genetic aberrations.
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| − | **#* Defects in synthesis are not commonly identified in the veterinary species.
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