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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)]]'''. It occurs in many veterinary species and can be primary or secondary.  

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.  

'''Primary hyperparathyroidism''' originates within the parathyroid gland itself and can be due to '''glandular hyperplasia or [[Neoplasia - Pathology|neoplasia]]'''. It is most commonly due to a '''solitary benign [[Adenoma|adenoma]]''' of either the [[Parathyroid Glands - Anatomy & Physiology|internal or external parathyroid gland]].<ref>Merck Veterinary Manual, '''Primary Hyperparathyroidism''', accessed online 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/40407.htm</ref>

<big>'''Primary hyperparathyroidism'''</big> originates within the parathyroid gland itself and can be due to '''glandular hyperplasia or [[Neoplasia - Pathology|neoplasia]]'''. It is most commonly due to a '''solitary benign [[Adenoma|adenoma]]''' of either the [[Parathyroid Glands - Anatomy & Physiology|internal or external parathyroid gland]].<ref>Merck Veterinary Manual, '''Primary Hyperparathyroidism''', accessed online 25/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/40407.htm</ref>

'''Secondary hyperparathyroidism''' can be either renal or nutritional in origin:

<big>'''Secondary hyperparathyroidism'''</big> 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'''. '''Reduced vitamin D''' synthesis is also thought to contribute to low serum calcium levels and subsequent stimulation of the parathyroid gland. 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'''. '''Reduced vitamin D''' synthesis is also thought to contribute to low serum calcium levels and subsequent stimulation of the parathyroid gland. Renal production of [[Calcium#Calcitriol|calcitriol]] is also reduced, exacerbating the resulting [[hypercalcaemia]].