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Patologia Endócrina em Equinos: a Disfunção da Pars Intermedia da Hipófise e o seu Impacto no Organismo
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A disfunção da pars intermedia da hipófise equina, também conhecida como Síndrome de Cushing, é
uma endocrinopatia comum em cavalos geriátricos, afetando 20% dos cavalos com mais de 15 (quinze)
anos e 25% dos com mais de 20 (vinte) anos. Esta patologia resulta da perda de inibição dopaminérgica
sobre a pars intermedia, devido à neurodegeneração dos neurónios dopaminérgicos hipotalâmicos,
levando à hiperplasia dos melanotrofos e à superprodução de pro-opiomelanocortina, convertida em
hormona adrenocorticotrópica, hormona estimulante de melanócitos alfa e β-endorfina. As variações
sazonais, nomeadamente o fotoperíodo, influenciam os níveis da hormona adrenocoticotropica e
hormona estimulante de melanócitos alfa, com picos no outono.
Os sinais clínicos desta disfunção incluem hipertricose (pelagem longa e densa), perda muscular,
abdómen pendular, depósitos adiposos localizados, laminite, letargia, poliúria/polidipsia,
imunossupressão (infeções oportunistas em 35% dos casos), distúrbios de fertilidade/lactação e
degeneração do ligamento suspensor do boleto.
O diagnóstico baseia-se na observação dos sinais clínicos, anamnese e testes como a medição de
hormona adrenocorticotrópica basal ou o teste de estimulação com hormona libertadora de
tireotropina.
O tratamento de eleição é o mesilato de pergolida, um agonista dopaminérgico D2, administrado por
via oral (0,002 mg/kg/dia), que normaliza a hormona adrenocorticotrópica e melhora os sinais clínicos
em 75% dos casos. Efeitos secundários (inapetência, cólicas) requerem ajuste gradual da dose. O
maneio inclui alimentação equilibrada, cuidados dentários, controlo parasitário e adaptações
ambientais (acesso à água, abrigo). A presença de laminite exige adicionalmente restrição de hidratos
de carbono não estruturais.
Sendo incurável, a disfunção da pars intermedia da hipófise requer tratamento vitalício. Um
diagnóstico precoce melhora o prognóstico, com uma esperança de vida de cerca de dez anos após o
diagnóstico, embora a hiperinsulinemia agrave o risco de laminite crónica. A colaboração entre
veterinários e proprietários é fundamental para uma gestão eficaz.
Equine dysfunction of the pars intermedia of the pituitary gland, also known as Cushing’s syndrome, is a common endocrine disorder in older horses. It affects approximately 20% of horses over 15 (fifteen) years and 25 % of those over 20 (twenty) years of age. This disease results from the loss of dopaminergic control over the pars intermedia of the pituitary gland, due to degeneration of dopamine-producing neurons in the hypothalamus. This leads to overgrowth of melanotrope cells and excessive production of pro-opiomelanocortin, a precursor molecule that is converted into adrenocorticotropic hormone, alpha-melanocyte-stimulating hormone, and beta-endorphin. Seasonal variations, particularly those related to day length, influence levels of adrenocorticotropic hormone and alpha-melanocyte-stimulating hormone, with peaks observed in the autumn. Clinical signs include hypertrichosis (long and dense coat), muscle wasting, a pendulous abdomen, localized fat deposits, laminitis, lethargy, increased urination and water intake, a weakened immune system (with opportunistic infections in 35% of cases), reproductive and lactation disorders, and degeneration of the supporting ligaments of the fetlock. Diagnosis is based on clinical signs, medical history, and specific tests such as measurement of resting adrenocorticotropic hormone levels or stimulation tests using thyrotropin-releasing hormone. The treatment of choice is mesylate of pergolide, a dopamine type 2 receptor agonist, administered orally (0,002 mg/kg/day). It helps normalize adrenocorticotropic hormone levels and improves clinical signs in approximately 75 % of cases. Side effects (such as loss of appetite or colic) may require gradual dose adjustment. Management also includes a balanced diet, dental care, parasite control, and environmental adjustments (such as access to clean water and shelter). In cases with laminitis, the intake of rapidly fermentable carbohydrates must be restricted. This disease is incurable and requires lifelong treatment. Early diagnosis improves the prognosis. On average, horses live for about ten years after diagnosis, although excessive insulin levels increase the risk of chronic laminitis. Close cooperation between veterinarians and horse owners is essential for successful management.
Equine dysfunction of the pars intermedia of the pituitary gland, also known as Cushing’s syndrome, is a common endocrine disorder in older horses. It affects approximately 20% of horses over 15 (fifteen) years and 25 % of those over 20 (twenty) years of age. This disease results from the loss of dopaminergic control over the pars intermedia of the pituitary gland, due to degeneration of dopamine-producing neurons in the hypothalamus. This leads to overgrowth of melanotrope cells and excessive production of pro-opiomelanocortin, a precursor molecule that is converted into adrenocorticotropic hormone, alpha-melanocyte-stimulating hormone, and beta-endorphin. Seasonal variations, particularly those related to day length, influence levels of adrenocorticotropic hormone and alpha-melanocyte-stimulating hormone, with peaks observed in the autumn. Clinical signs include hypertrichosis (long and dense coat), muscle wasting, a pendulous abdomen, localized fat deposits, laminitis, lethargy, increased urination and water intake, a weakened immune system (with opportunistic infections in 35% of cases), reproductive and lactation disorders, and degeneration of the supporting ligaments of the fetlock. Diagnosis is based on clinical signs, medical history, and specific tests such as measurement of resting adrenocorticotropic hormone levels or stimulation tests using thyrotropin-releasing hormone. The treatment of choice is mesylate of pergolide, a dopamine type 2 receptor agonist, administered orally (0,002 mg/kg/day). It helps normalize adrenocorticotropic hormone levels and improves clinical signs in approximately 75 % of cases. Side effects (such as loss of appetite or colic) may require gradual dose adjustment. Management also includes a balanced diet, dental care, parasite control, and environmental adjustments (such as access to clean water and shelter). In cases with laminitis, the intake of rapidly fermentable carbohydrates must be restricted. This disease is incurable and requires lifelong treatment. Early diagnosis improves the prognosis. On average, horses live for about ten years after diagnosis, although excessive insulin levels increase the risk of chronic laminitis. Close cooperation between veterinarians and horse owners is essential for successful management.
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Disfunção da pars intermedia da hipófise Equinos Neurodegenerescencia dopaminergica Pergolide Sindrome de Cushing Cushing's syndrome Dopaminergic neurodegeneration Dysfunction of the pars intermedia of the pituitary gland Horses