Restored vision in a young dog following corticosteroid treatment of presumptive hypophysitis

Lymphocytic Panhypophysitis Resulting in Panhypopituitarism in a Dog

A 3 yr old intact male Doberman pinscher was referred with chronic diarrhea, severe polyuria-polydipsia, and behavioral changes for 2 wk. Biochemical abnormalities were consistent with central diabetes insipidus, hypothyroidism, and hypoadrenocorticism. Brain MRI and cerebrospinal fluid analysis raised suspicion for lymphocytic hypophysitis and meningitis, later confirmed histologically. Immunosuppressive steroid therapy and hormonal supplementation were implemented, resulting in a marked clinical improvement. Brain MRI at a 3 mo follow-up showed a resolution of inflammatory lesions along with pituitary atrophy. The patient was euthanized 4.5 mo following diagnosis because of uncontrolled aggressiveness. Lymphocytic hypophysitis (LHP) is a rare autoimmune condition in people and dogs, often accompanied by total or partial pituitary hormonal deficiency. This is the first case of histologically confirmed canine LHP with documented clinical and biochemical response to medical management. As described in people, LHP should be considered as a differential diagnosis for pituitary lesions. Although the overall prognosis of this disease remains guarded to poor, early diagnosis and adequate immunosuppressive treatment might improve the outcome.

Transsphenoidal Surgery for Pituitary Tumors

Transsphenoidal surgery for the treatment of pituitary masses in cats and dogs has become a more established treatment over the last 2 decades. Although expert centers and surgeons that provide this service remain limited, the patient population presented for pituitary surgery increases with wider availability of advanced imaging, together with more challenging cases. In this review, the current state of hypophysectomy is described with future challenges and opportunities.

Pituitary tumour types in dogs and cats

Pituitary tumours are common in dogs and are being increasingly recognized in cats. Pituitary tumours are usually classified as adenomas and should only be classified as carcinomas when there is evidence of metastatic spread of the tumour, which is rare. Despite the benign nature of most pituitary tumours, they can still compress or invade neighbouring tissues. Pituitary tumours can be functional (hormonally active) or non-functional (hormonally silent). The aim of this review was to provide an overview of the different pituitary tumour types in dogs and cats that have been reported in the literature. In dogs, the most common pituitary tumour type is the corticotroph adenoma, which can cause pituitary-dependent hypercortisolism. In cats, the most common pituitary tumour is the somatotroph adenoma, which can cause hypersomatotropism, and the second-most common is the corticotroph adenoma. A lactotroph adenoma has been described in one dog, while gonadotroph, thyrotroph and null cell adenomas have not been described in dogs or cats. Hormonally silent adenomas are likely underdiagnosed because they do not result in an endocrine syndrome. Tools used to classify pituitary tumours in humans, particularly immunohistochemistry for lineage-specific transcription factors, are likely to be useful to classify canine and feline pituitary tumours of unknown origin. Future studies are required to better understand the full range of pituitary adenoma pathology in dogs and cats and to determine whether certain adenoma subtypes behave more aggressively than others. Currently, the mechanisms that underlie pituitary tumorigenesis in dogs and cats are still largely unknown. A better understanding of the molecular background of these tumours could help to identify improved pituitary-targeted therapeutics.

Variation in the MRI appearance of the canine pituitary gland

A recent publication described pathological findings in the pituitary gland incidentally discovered during routine necropsies of the brain of dogs and cats; however, imaging characteristics of these lesions were not reported. Aims of this retrospective, observational study were to characterize MRI variants and incidental lesions in pituitary glands of dogs with no clinical signs of pituitary disease. Cranial MRIs from dogs with no suspicion of pituitary disease, based on history and presenting clinical signs, were retrieved from a veterinary teleradiology database during the period of January 2014 to January 2016. Images were reinterpreted by two observers and pituitary lesions were described based on consensus. A total of 580 scans were evaluated and pituitary lesions were detected in 78 dogs (13.44%). Pituitary cystic lesions were the most common finding and occurred in 31 dogs (5.34%). Of these 31 dogs, the majority (74%) were of toy or brachycephalic breed. Partial or total empty sella lesions were detected in 14 dogs (2.41%), and all of these were small or toy breeds. A significantly increased incidence of the partial empty sella lesion was found in male dogs (P = .034). Pituitary lesions greater than 1 cm occurred rarely (0.69%). There was a significant association between low-field (LF) MRI strength and detection of a partial or total empty sella lesion (P = .0112), and detection of a pituitary lesion greater than 1 cm (P = .0125). A significant difference was present between the MRI field strength (FS) that identified pituitary cysts and the FS that detected an empty sella (P = .0068), with the former being a high FS and the latter a LF strength. The findings from this study indicated that up to 13% of dogs with no presenting clinical signs of pituitary disease may have MRI pituitary lesions.

Pathological Findings in the Pituitary Glands of Dogs and Cats

With the exception of classic functional adenomas in dogs and horses, pituitary lesions are infrequently described in the veterinary literature. Approximately 10% of pituitary glands from asymptomatic humans contain abnormalities, but the equivalent proportion in small animals is unknown. Pituitary glands from 136 dogs and 65 cats collected during routine necropsies were examined to determine the prevalence of pituitary lesions and their histopathological diagnosis. Lesions were characterized in sections stained with hematoxylin and eosin, periodic acid-Schiff (PAS), Gordon and Sweet’s and reticulin stains, and immunohistochemistry for adrenocorticotropic hormone (ACTH), growth hormone, melanocyte stimulating hormone–α, and prolactin. Pituitary abnormalities were identified in 36 of 136 (26.4%) dogs and 10 of 65 (15.3%) cats. Cystic changes were the most common lesion, occurring in 18 (13.2%) dogs and 8 (12.3%) cats. Pituitary neoplasia was detected in 14.1% (12/85) of middle-aged and old dogs; 1 (1.5%) cat had pituitary nodular hyperplasia. PAS and reticulin stains helped differentiate ACTH-immunoreactive adenomas from hyperplastic nodules: adenomas contained PAS-positive intracytoplasmic granules and loss of the normal reticulin network. One dog had a pituitary carcinoma with infiltration into the thalamus. Other pituitary abnormalities included secondary metastases (2 dogs) and hypophysitis (4 dogs, 1 cat). In most cases, the lesion appeared to be subclinical and could be considered incidental, whereas clinical manifestations were apparent in only 4 dogs (2.9%) and none of the cats with pituitary lesions. Pituitary abnormalities are common in dogs and cats, and their clinical relevance requires further investigation.

Hypophysitis, Panhypopituitarism, and Hypothalamitis in a Scottish Terrier Dog

A 6‐year old male neutered Scottish Terrier was referred with a 1 week history of progressive lethargy and anorexia. Neurological examination localized a lesion to the forebrain and hormonal testing showed panhypopituitarism. Magnetic resonance imaging (MRI) of the brain revealed a rounded, well‐defined, suprasellar central mass. The mass was slightly hyperintense to the cortical grey matter on T2‐weighted (T2W), hypointense on T1‐weighted (T1W) images and without T2* signal void. There was a central fusiform enhancement of the mass after contrast administration which raised the suspicion of a pituitary neoplasm. Rapid deterioration of the dog prevented further clinical investigations. Histopathologic examination revealed a lymphocytic panhypophysitis of unknown origin suspected autoimmune involving the hypothalamus (hypothalamitis). This is a unique case report of a dog presenting with inflammatory hypophysitis and hypothalamitis of suspected autoimmune origin with detailed clinical, MRI, histology and immunohistochemistry findings.