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Also Known As – '''''Parathyroid hyperplasia – Parathyroid adenoma - Fibrous Osteodystrophy – Grain Overload – Bran Disease – Bran-head Disease – Rubber Jaw '''''
Also Known As – '''''Parathyroid hyperplasia – Parathyroid adenoma - Fibrous Osteodystrophy – Grain Overload – Bran Disease – Big Head Disease – Millers Disease - Rubber Jaw '''''
==Introduction==
==Introduction==
Secondary hyperparathyroidism can be either renal or nutritional in origin:
Secondary hyperparathyroidism can be either renal or nutritional in origin:
Secondary renal hyperparathyroidism is a complication of chronic renal failure. This is due to hyperphosphataemia developing as a result of impaired glomerular filtration rate. Renal production of [[Calcium#Calcitriol#calcitriol]] is also reduced, exacerbating the resulting hypercalcaemia.
Secondary renal hyperparathyroidism is a complication of chronic renal failure. This is due to hyperphosphataemia developing as a result of impaired glomerular filtration rate. Renal production of [[Calcium#Calcitriol|calcitriol]] is also reduced, exacerbating the resulting hypercalcaemia.
Secondary nutritional hyperparathyroidism is caused by excessive phosphorus intake causing a total or relative calcium deficiency by binding calcium in the gut and decreasing its absorption. This encompasses bran disease in horses and also [[Metabolic Bone Disease|metabolic bone disease]] in reptiles.
==Signalment==
==Signalment==
Secondary renal hyperparathyroidism is seen frequently in dogs and occasionally in cats.
Secondary renal hyperparathyroidism is seen frequently in dogs and occasionally in cats.
Nutritional secondary HPT can affect horses of all breeds and ages that are either supplemented with large amounts of grain based concentrates or bran, or those that escape and break into a grain store or similar.
Metabolic Bone Disease occurs in a wide range of reptiles.
==Clinical Signs==
==Clinical Signs==
The main effect of hyperparathyroidism is [[Hypercalcaemia|hypercalcaemia]] which causes a range of clinical signs. Polydipsia, polyuria, anorexia, lethargy and depression are the most common signs but animals may also be constipated, weak, stiff-gaited, shivering and vomiting. Mild hypercalcaemia may not generate any overt clinical signs.
The main effect of hyperparathyroidism is [[Hypercalcaemia|hypercalcaemia]] which causes a range of clinical signs. Polydipsia, polyuria, anorexia, lethargy and depression are the most common signs but animals may also be constipated, weak, stiff-gaited, shivering and vomiting. Mild hypercalcaemia may not generate any overt clinical signs.
Sequelae of hyperparathyroidism include fibrous osteodystrophy and
Sequelae of hyperparathyroidism include fibrous osteodystrophy and
Osteodystrophy is the [[Bone - Anatomy & Physiology#Osteoclasts|osteoclastic resorption]] of bone and replacement by weaker fibrous tissue. When this occurs in the long bones it causes lameness and weakened bones that are prone to [[Fractures|fracture]]. Compression fractures may also occur spontaneously and if this occurs in the vertebrae, nerve dysfunction results.<ref>Merck Veterinary Manual, '''Metabolic Osteodystrophies: Fibrous Osteodystrophy: Primary Hyperparathyroidism''', accessed online 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/90313.htm</ref>
Osteodystrophy is the [[Bone - Anatomy & Physiology#Cells|osteoclastic resorption]] of bone and replacement by weaker fibrous tissue. When this occurs in the long bones it causes shifting lameness and weakened bones that are prone to [[Fractures|fracture]]. Compression fractures may also occur spontaneously and if this occurs in the vertebrae, nerve dysfunction results.<ref>Merck Veterinary Manual, '''Metabolic Osteodystrophies: Fibrous Osteodystrophy: Primary Hyperparathyroidism''', accessed online 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/90313.htm</ref>
Fibrous osteodystrophy in the flat bones of the skull and face causes facial hyperostosis. This is seen in Bran disease or grain overload in horses and also in dogs with primary hyperparathyroidism. The face and head become grossly disfigured by excessive amounts of fibrous tissue laid down in an attempt to consolidate the weakened lamellar bone. In advanced cases, the mandible may become pliant and teeth may loosen, hence the colloquial name, “rubber jaw”.
Fibrous osteodystrophy in the flat bones of the skull and face causes facial hyperostosis. This is seen in Bran disease or grain overload in horses and also in dogs with primary hyperparathyroidism. The face and head become grossly disfigured by excessive amounts of fibrous tissue laid down in an attempt to consolidate the weakened lamellar bone. In advanced cases, the mandible may become pliant and teeth may loosen, hence the colloquial name, “rubber jaw”. This may interfere with mastication and cause pain, dysphagia and consequent weight loss.
Animals affected by secondary renal HPT may exhibit classical signs of renal insufficiency such as polydipsia, polyuria, weight loss, vomiting and dehydration.
Animals affected by secondary renal HPT may exhibit classical signs of renal insufficiency such as polydipsia, polyuria, weight loss, vomiting and dehydration.
Exploratory surgery of the cervical region may identify enlarged parathyroid glands if no other test is available or confirmatory.
Exploratory surgery of the cervical region may identify enlarged parathyroid glands if no other test is available or confirmatory.
In cases of nutritional hyperparathyroidism, serum calcium is normal or low compared to high in other pathogeneses. Urinary excretion of phosphorus is markedly increased and serum PTH high. Radiographs will identify bony resorption and pathological fractures with fibrous tissue calluses.
==Treatment==
==Treatment==
Treatment for primary hyperparathyroidism usually required surgical excision. Hypocalcaemia is a known post-operative complication and supplementation may be required in the short or long term management. If the hypercalcaemia persists, metastatic disease should be suspected and investigated.
Treatment for primary hyperparathyroidism usually required surgical excision. Hypocalcaemia is a known post-operative complication and supplementation may be required in the short or long term management. If the hypercalcaemia persists, metastatic disease should be suspected and investigated.
Renal secondary HPT therapy is directed at control of the renal disease by way of specialised diet and rehydration along with supplementation of calcitriol and phosphorus binders.
Renal secondary HPT therapy is directed at control of the renal disease by way of specialised diet and rehydration along with supplementation of calcitriol and phosphorus binders.
Horses with bran disease should be confined until radiographs show normal bone density. Diet should be rectified if inadequate, and calcium: phosphorus ratio maintained at 1:1-3:1 for the first 2-3 months followed by a normal ration. If horses have also been feeding on plants high in oxalates (which can also bind calcium in the intestine) then these should be removed from the diet and limestone can be added to the diet to prevent or treat any associating signs.
{{Learning
{{Learning
==References==
==References==
<references/>
<references/>
Lavoie, J-P., Hinchcliff, K. W (2008) '''Blackwell’s Five-Minute Veterinary Consult: Equine 2nd ed'''. ''Wiley-Blackwell, Oxford'', pp.
Lavoie, J-P., Hinchcliff, K. W (2008) '''Blackwell’s Five-Minute Veterinary Consult: Equine 2nd ed'''. ''Wiley-Blackwell, Oxford'', pp524-525.
Merck Vet Manual, Renal Secondary Hyperparathyroidism, accessed 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/90314.htm
Merck Vet Manual, Renal Secondary Hyperparathyroidism, accessed 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/90314.htm
Merck Vet Manual, Nutritional Diseases, accessed 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/182606.htm&word=nutritional%2csecondary
[[Category:To Do - Manson review]] [[Category: Endocrine Diseases - Horse]] [[Category: Endocrine Diseases - Dog]] [[Category: Endocrine Diseases - Cat]] [[Category: Endocrine Diseases - Reptile]]
[[Category:To Do - Manson review]] [[Category: Endocrine Diseases - Horse]] [[Category: Endocrine Diseases - Dog]] [[Category: Endocrine Diseases - Cat]] [[Category: Endocrine Diseases - Reptile]]