Pituitary <i>pars intermedia</i> dysfunction in horses associated to pituitary adenoma

The clinical syndrome of the pituitary pars intermedia dysfunction (PPID) is the most common endocrinopathy of older horses. This syndrome is characterized by several clinical and pathological changes, which are usually associated with adenomas of the pars intermedia (PI) of the pituitary gland. The aim of this work is to describe five cases of pituitary adenoma of the PI associated with PPID in horses, addressing its clinical and pathological aspects. The horses had a mean of 22 years of age. The main clinical signs were hirsutism and paresis of hind limbs, and at post mortem examination all horses had hirsutism, and a nodule in the pituitary gland, which was histologically characterized as an adenoma of PI (5/5). Furthermore, two horses had gross lesions suggestive of chronic laminitis. Moreover, there was intense parasitism of Sarcocystis neurona (2/5), Strongylus vulgaris (1/5), Parascaris equorum (1/5), Draschia megastoma (1/5), and Klossiella equi (1/5).

INDEX TERMS:
PPID; hypothalamus; parasitism; hirsutism; laminitis; horses; equine

Authorship

Anderson H. Gris ^**Corresponding author: anderson_gris@hotmail.com.br

Setor de Patologia Veterinária, Faculdade de Veterinária (FAVET), Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9090, Porto Alegre, RS 91540-000, Brazil.Universidade Federal do Rio Grande do SulBrazilPorto Alegre, RS, BrazilSetor de Patologia Veterinária, Faculdade de Veterinária (FAVET), Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9090, Porto Alegre, RS 91540-000, Brazil.

http://orcid.org/0000-0002-3926-9491

Ronaldo M. Bianchi

http://orcid.org/0000-0001-9187-486X

Claiton I. Schwertz

http://orcid.org/0000-0002-5285-7896

Manoela M. Piva

http://orcid.org/0000-0002-1484-2220

Gabriela Richter

Centro Universitário Ritter dos Reis (UniRitter), Av. Manoel Elias 2001, Alto Petrópolis, Porto Alegre, RS 91240-261, Brazil.Centro Universitário Ritter dos ReisBrazilPorto Alegre, RS, BrazilCentro Universitário Ritter dos Reis (UniRitter), Av. Manoel Elias 2001, Alto Petrópolis, Porto Alegre, RS 91240-261, Brazil.

http://orcid.org/0000-0002-2847-7914

Luciana Sonne

http://orcid.org/0000-0003-3101-8134

David Driemeier

http://orcid.org/0000-0003-3766-0654

Saulo P. Pavarini

http://orcid.org/0000-0001-8980-6294

*Corresponding author: anderson_gris@hotmail.com.br

Conflict of interest statement.- The authors declare having no conflicts of interest.

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (2)
Tables (1)

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Fig.1-2.
Macroscopic findings of horses with pituitary pars intermedia dysfunction (PPID). (1) Horse 3 with excessively long, thick, and wavy hair and poorly body condition, with marked loss of muscle mass. (2) Head, cut surface (Horse 3). Pituitary gland markedly enlarged, showing a white to light brown mass, with multifocal interspersed dark red areas compressing the glandular parenchyma and the overlying hypothalamus.

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Fig.3-6.
Histological findings of horses with pituitary pars intermedia dysfunction (PPID). (3) Pituitary gland (Horse 3). A multilobulated, partially encapsulated and delimited neoplastic proliferation of well differentiated epithelial cells of pars intermedia, almost completely replaces the pituitary parenchyma and compresses pars distalis and pars nervosa. HE, obj.4x. (4) Pituitary gland (Horse 3). The neoplastic cells are arranged in cords or nests separated by fine septa of fibrovascular stroma. These cells were polyhedral and frequently assumed a pseudorosette form around blood vessels. HE, obj.20x. (5) Brain (pons, Horse 3). Area of severe necrosis, associated with a severe inflammatory infiltrate of neutrophils, lymphocytes, macrophages, and occasional eosinophils, in addition to substantial amounts of parasitic structures morphologically compatible with schizonts and merozoites of Sarcocystis neurona. HE, obj.40x. Inset: There is marked immunolabeling of the parasitic structure. Anti-S. neurona. IHC, obj.60x. (6) Kidney (Horse 3). Parasitic structures of Klossiela equi in the tubular epithelium, characterized by rounded light basophilic sporonts of 80 to 150μm, with multiple round and basophilic dots of 10μm and disposed in a radiated pattern (sporoblasts). There are oval-shaped amphophilic structures of 10 to 20μm with abundant basophilic dots compatible with mature sporocysts with sporoblasts. There is also mild multifocal interstitial inflammatory infiltrate of lymphocytes, plasma cells and macrophages. HE, obj.20x.

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Table 1.
Identification, clinical history, and cause of death of the five horses with PPID syndrome

Fig.1-2. Macroscopic findings of horses with pituitary pars intermedia dysfunction (PPID). (1) Horse 3 with excessively long, thick, and wavy hair and poorly body condition, with marked loss of muscle mass. (2) Head, cut surface (Horse 3). Pituitary gland markedly enlarged, showing a white to light brown mass, with multifocal interspersed dark red areas compressing the glandular parenchyma and the overlying hypothalamus.

Fig.3-6. Histological findings of horses with pituitary pars intermedia dysfunction (PPID). (3) Pituitary gland (Horse 3). A multilobulated, partially encapsulated and delimited neoplastic proliferation of well differentiated epithelial cells of pars intermedia, almost completely replaces the pituitary parenchyma and compresses pars distalis and pars nervosa. HE, obj.4x. (4) Pituitary gland (Horse 3). The neoplastic cells are arranged in cords or nests separated by fine septa of fibrovascular stroma. These cells were polyhedral and frequently assumed a pseudorosette form around blood vessels. HE, obj.20x. (5) Brain (pons, Horse 3). Area of severe necrosis, associated with a severe inflammatory infiltrate of neutrophils, lymphocytes, macrophages, and occasional eosinophils, in addition to substantial amounts of parasitic structures morphologically compatible with schizonts and merozoites of Sarcocystis neurona. HE, obj.40x. Inset: There is marked immunolabeling of the parasitic structure. Anti-S. neurona. IHC, obj.60x. (6) Kidney (Horse 3). Parasitic structures of Klossiela equi in the tubular epithelium, characterized by rounded light basophilic sporonts of 80 to 150μm, with multiple round and basophilic dots of 10μm and disposed in a radiated pattern (sporoblasts). There are oval-shaped amphophilic structures of 10 to 20μm with abundant basophilic dots compatible with mature sporocysts with sporoblasts. There is also mild multifocal interstitial inflammatory infiltrate of lymphocytes, plasma cells and macrophages. HE, obj.20x.

Table 1. Identification, clinical history, and cause of death of the five horses with PPID syndrome

Case	Breed	Sex/Age	History and clinical features	Cause of death
Horse 1	Crioulo	Female/26 years	Hirsutism, polyphagia and colic signs, submitted to exploratory laparotomy, showing gastric and intestinal distention, which was reduced in surgery. However, the horse did not recover.	Gastric rupture
Horse 2	Anglo Arabian	Female/30 years	Hirsutism for a year, polyphagia, laminitis treatment for three weeks, and after that, started to present generalized loss of muscle mass, tetraparesis, ataxia, nystagmus, hypothermia, progressive weakness and progressed to lateral decubitus.	Euthanasia due to neurologic signs (presumably to equine protozoal myeloencephalitis)
Horse 3	Crioulo	Male/20 years	Hirsutism, polyphagia, and muscle loss during a year. The last month before the euthanasia, the horse showed incoordination of hind limbs, that progressed to paresis, blindness, and decubitus.	Euthanasia due to neurologic signs (presumably to equine protozoal myeloencephalitis)
Horse 4	Thoroughbred	Female/18 years	Hirsutism, polyphagia, and hyperhidrosis for a year before the euthanasia. A week before the death it starts to present incoordination, circling walk and emaciation.	Euthanasia due to neurologic signs
Horse 5	Mixed breed	Female/16 years	Hirsutism without time history and was found in decubitus two days before the euthanasia, as it did not recover. Also presented polyphagia.	Euthanasia due to decubitus and poor prognosis

PPID = pituitary pars intermedia dysfunction.

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Pituitary <i>pars intermedia</i> dysfunction in horses associated to pituitary adenoma

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[1] *Corresponding author: anderson_gris@hotmail.com.br