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[[Image:Renal_osteodystrophy.jpg|thumb|right|200px|"Rubber jaw" in renal osteodystrophy. Image courtesy of Biomed Archive.]]
 
[[Image:Renal_osteodystrophy.jpg|thumb|right|200px|"Rubber jaw" in renal osteodystrophy. Image courtesy of Biomed Archive.]]
 
[[Image:parathyroidhyperplasia.jpg|thumb|right|200px|Parathyroid hyperplasia. Image courtesy of Biomed Archive.]]
 
[[Image:parathyroidhyperplasia.jpg|thumb|right|200px|Parathyroid hyperplasia. Image courtesy of Biomed Archive.]]
Hyperparathyroidism is an '''[[Endocrine System - Anatomy & Physiology|endocrine]] disease''' caused by overactivity of the [[Parathyroid Glands - Anatomy & Physiology|parathyroid gland]] and consequent '''raised body levels of [[Calcium#Parathyroid Hormone|parathyroid hormone (PTH)]]'''. It occurs in many veterinary species and can be primary or secondary.  
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Hyperparathyroidism is an '''[[Endocrine System - Anatomy & Physiology|endocrine]] disease''' caused by overactivity of the [[Parathyroid Glands - Anatomy & Physiology|parathyroid gland]] and consequent '''raised body levels of [[Calcium#Parathyroid Hormone|parathyroid hormone (PTH)]]'''. This in turn results in chronic hypercalaemia. It occurs in many veterinary species and can be primary or secondary.  
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<big>'''Secondary hyperparathyroidism'''</big> is usually diffuse hyperplasia of the parathyroid glands and can be either renal or nutritional in origin:
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<big>'''Secondary hyperparathyroidism'''</big> is usually diffuse hyperplasia of the parathyroid glands due to relative hypocalcaemia and can be either renal or nutritional in origin:
    
Secondary '''renal hyperparathyroidism''' is a complication of '''chronic renal failure'''. This is due to relative '''hyperphosphataemia developing as a result of impaired glomerular filtration rate'''. '''Reduced vitamin D''' synthesis or absorbtion is also thought to contribute to low serum calcium levels and subsequent stimulation of the parathyroid gland. Renal production of [[Calcium#Calcitriol|calcitriol]] (active Vitamin D3) is also reduced, exacerbating the resulting [[hypercalcaemia]].  
 
Secondary '''renal hyperparathyroidism''' is a complication of '''chronic renal failure'''. This is due to relative '''hyperphosphataemia developing as a result of impaired glomerular filtration rate'''. '''Reduced vitamin D''' synthesis or absorbtion is also thought to contribute to low serum calcium levels and subsequent stimulation of the parathyroid gland. Renal production of [[Calcium#Calcitriol|calcitriol]] (active Vitamin D3) is also reduced, exacerbating the resulting [[hypercalcaemia]].