Changes

==Introduction==

==Introduction==

PPID is a slowly-progressive disorder of the horse with a characteristic clinical picture. It is associated with '''functional adenomas''' or '''adenomatous hyperplasia of the pars intermedia of the pituitary gland'''.

PPID is a slowly-progressive disorder of the horse with a characteristic clinical picture. It is associated with '''functional adenomas''' or '''adenomatous hyperplasia of the pars intermedia of the [[Pituitary Gland - Anatomy & Physiology|pituitary gland]]'''.

It affects all breeds of horses but is more common in '''ponies''' and Morgans. It occurs in '''older horses, between 10 and 30 years with a mean of 20 years'''. There are no sex predilections.

It affects all breeds of horses but is more common in '''ponies''' and Morgans. It occurs in '''older horses, between 10 and 30 years with a mean of 20 years'''. There are no sex predilections.

'''Presenting signs include''': '''weight loss or muscle wasting''', decreased muscle tone, abnormal bulging of supraorbital fat pads: catabolism promoted

'''Presenting signs include''': '''weight loss or muscle wasting''', decreased muscle tone, abnormal bulging of supraorbital fat pads: catabolism promoted

A '''thick, long and wavy hair coat''' with an abnormal shedding pattern is evident in 85% of affected horses. This sign is often preceeded by months to years of subtle coat variations, such as patchy slow shedding during late spring or delayed shedding with alopecia.

A '''thick, long and wavy hair coat''' with an abnormal shedding pattern is evident in 85% of affected horses. This sign is often preceded by months to years of subtle coat variations, such as patchy slow shedding during late spring or delayed shedding with alopecia.

'''Polyuria and polydipsia''': insulin antagonism, hyperglycaemia and osmotic diuresis, and ADH antagonism

'''Polyuria and polydipsia''': due to insulin antagonism, hyperglycaemia and osmotic diuresis, and [[Pituitary Gland - Anatomy & Physiology#Antidiuretic Hormone|ADH]] antagonism

'''Lethargy'''

'''Lethargy'''

'''Persistent sweating'''

'''Persistent sweating'''

'''Chronic recurrent laminitis''': digital vasoconstrictive effects of catecholamines

'''Chronic recurrent [[Laminitis - Horse|laminitis]]''': due to digital vasoconstrictive effects of catecholamines

'''Chronic recurrent skin, pulmonary, urinary, or sinus infections''': immunosuppression

'''Chronic recurrent skin, pulmonary, urinary, or sinus infections''': due to immunosuppression

'''Vision disturbances''': central effects

'''Vision disturbances''': central effects

==Diagnosis==

==Diagnosis==

'''Plasma cortisol concentration''': there is a wide variation in normal values and it is not useful in diagnosing the condition.

'''Plasma cortisol concentration''' can be measures but there is a wide variation in normal values and it is not useful in diagnosing the condition.

'''The dexamethasone suppression test''' is the gold standard for diagnosis of the disease. Plasma cortisol samples are taken before and after dexamethasone administration. Normal horses will show a level of cortisol below 1 μg/dL 19 hours after dexamethasone administration, whereas affected horses will show a small degree of suppression in cortisol levels, but not to the level of normal horses, and levels also rebound more quickly.

'''The dexamethasone suppression test''' is the gold standard for diagnosis of the disease. Plasma cortisol samples are taken before and after dexamethasone administration. Normal horses will show a level of cortisol below 1 μg/dL 19 hours after dexamethasone administration, whereas affected horses will show a small degree of suppression in cortisol levels, but not to the level of normal horses, and levels also rebound more quickly.

A variety of other tests exist to evaluate horses for PPID:

A variety of other tests exist to evaluate horses for PPID:

 

:'''ACTH stimulation test, resting ACTH level, TRH stimulation test, glucose tolerance test, insulin levels and insulin tolerance test'''

'''ACTH stimulation test, resting ACTH level, TRH stimulation test, glucose tolerance test, insulin levels and insulin tolerance test'''

None of these are of greater sensitivity or specificity than the dexamethasone suppression test and are frequently less convenient to perform and more expensive.

None of these are of greater sensitivity or specificity than the dexamethasone suppression test and are frequently less convenient to perform and more expensive.

The only disadvantage of the dexamethasone suppression test is the reported increased risk of laminitis.

The only disadvantage of the dexamethasone suppression test is the reported increased risk of laminitis. In at risk cases, '''ACTH levels''' are nearly as sensitive in diagnosing the condition.

 

In at risk cases, '''ACTH levels''' are nearly as sensitive in diagnosing the condition.

 

'''Haematology and biochemistry''' may reveal: hyperglycaemia and hyperlipidaemia. Liver enzymes may be elevated due to hepatic lipidosis secondary to the lipolysis. There may be a stress leukogram.

'''Haematology and biochemistry''' may reveal hyperglycaemia and hyperlipidaemia. Liver enzymes may be elevated due to [[Hepatic Lipidosis|hepatic lipidosis]] secondary to the lipolysis. There may be a [[Stress Leucogram|stress leukogram]].

==Treatment==

==Treatment==

Treatment can be difficult due to the age of the animal and the multiple problems which can occur in a given animal.  

Treatment can be difficult due to the age of the animal and the multiple problems which can occur in a given individual.  

In some animals, there may be '''unacceptable pain''' from laminitis, or marked debilitation from the muscle wasting and '''euthanasia''' may be the humane decision.

In some animals, there may be '''unacceptable pain''' from laminitis, or marked debilitation from the muscle wasting and '''euthanasia''' may be the humane decision.

Other cases may be managed by '''supportive therapy''':  

Other cases may be managed by '''supportive therapy''':  

:Treating any '''infections''': skin and respiratory

:Treating any '''infections''' (skin and respiratory)

:Maintaining a '''high plane of nutrition'''

:Maintaining a '''high plane of nutrition'''

:Hoof care for mild laminitis, or '''NSAIDs''' if needed

:Hoof care for mild laminitis, or '''[[NSAIDs]]''' if needed

:'''Clipping''' to remove long hair

:'''Clipping''' to remove long hair

These cases may have an acceptable quality of life for several years.

These cases may have an acceptable quality of life for several years.

:'''Cyproheptadine''': a serotonin antagonist, was one of the first drugs used for the disease. The response is variable

:'''Cyproheptadine''': a serotonin antagonist, was one of the first drugs used for the disease. The response is variable

:'''Bromocriptine''': dopaminergic agonist, to replace loss of dopaminergic innervation. The bioavailability of the drug is low.

:'''Bromocriptine''': dopaminergic agonist, to replace loss of dopaminergic innervation. The bioavailability of the drug is low.

:'''Pergolide''': dopaminergic agonist, therapy of choice. Clinical improvement occurs in a few weeks in approximately 80% of cases. Doses can be increased if signs are still apparent, but treatment should be stopped if diarrhoea, anorexia and worsening laminitis occur.

:'''Pergolide''': dopaminergic agonist, '''therapy of choice'''. Clinical improvement occurs in a few weeks in approximately 80% of cases. Doses can be increased if signs are still apparent, but treatment should be stopped if diarrhoea, anorexia and worsening laminitis occur.

:'''Trilostane''': inhibits 3-beta-hydroxysteroid dehydrogenase. Used in Canine Cushing's, but variable results in horses.

:'''Trilostane''': inhibits 3-beta-hydroxysteroid dehydrogenase. It is used in [[Hyperadrenocorticism|Canine Cushing's]] but gives variable results in horses.

==Prognosis==

==Prognosis==

[[Category:To Do - Helen]]

[[Category:To Do - Review]]

[[Category:Endocrine Diseases - Horse]]

[[Category:Expert Review - Horse]]