Functional and Morphological Changes in the Hypothalamus-Pituitary Posterior Lobe System after Hypophysectomy in the Dog

Taoda, Takahiro; Hara, Yasushi; Masuda, Hiroyuki; Nezu, Yoshinori; Sanno, Naoko; Teramoto, Akira; Takekoshi, Susumu; Osamura, R. Yoshiyuki; Tagawa, Masahiro

doi:10.1292/jvms.68.1

Cited by 5 publications

(5 citation statements)

References 25 publications

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“…57 However, Taoda et al reported that the AVP secretion ability did not sufficiently recover in healthy dogs even at 3 months after the TSS procedure. 58 An explanation for this may be the possible involvement of compensatory mechanisms such as V 2 receptor upregulation in the kidney. In addition to DDAVP, hormone replacement therapy with two drugs (glucocorticoids and thyroid hormone) is necessary after TSS.…”

Section: CDImentioning

confidence: 99%

<p>Transsphenoidal Surgery in Canines: Safety, Efficacy and Patient Selection</p>

Hara¹

2020

VMRR

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Pituitary-dependent hyperadrenocorticism (PDH) is the cause of approximately 80-85% of naturally occurring cases of hyperadrenocorticism(HAC) in canines and is triggered by an adrenocorticotropic hormone (ACTH)-producing pituitary adenoma or hyperplasia of the corticotroph in the pituitary anterior lobe or intermediate lobe. Transsphenoidal surgery(TSS) is an effective treatment that can directly remove pituitary tumors that cause PDH in canines under a single course of general anesthesia. However, careful evaluations of the definitive diagnosis, adenoma size and growth rate, relationship with surrounding tissue, general condition, and neurosurgical procedural skill involved in each case are important to determine TSS suitability. The basic principle is to confirm that the present HAC case is PDH, that is, an ACTH-producing adenoma or the hyperplasia of the corticotroph originating from either the pituitary anterior or intermediate lobe. Evaluations based on endocrinology, particularly plasma ACTH concentration, and imaging diagnosis, particularly MRI is essential for definitive diagnosis. Enlarged pituitary tumors can shorten the post-TSS survival time, increase the recurrence rate of clinical symptoms, and increase the risk for developing permanent central diabetes insipidus. Therefore, complete removal of adenomas of up to Grade IIIA according to the MRI-based classification system is relatively easy to achieve with TSS, and long-term remission and survival can be expected.

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Section: CDImentioning

confidence: 99%

<p>Transsphenoidal Surgery in Canines: Safety, Efficacy and Patient Selection</p>

Hara¹

2020

VMRR

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“…However, other compensatory mechanisms might play important roles in resuming the activity of AVP, and some of these have not yet been fully investigated. 20 …”

Section: Discussionmentioning

confidence: 99%

Plasma sodium and potassium concentrations after hypophysectomy in dogs with corticotroph adenomas

Magno

Rijn

Azzariti

et al. 2021

Veterinary Internal Medicne

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Background Electrolyte abnormalities, especially hypernatremia, are frequent complications after transsphenoidal hypophysectomy in dogs with pituitary‐dependent hypercortisolism. Objectives To describe electrolyte abnormalities after transsphenoidal hypophysectomy and to investigate possible associations between postoperative hypernatremia and clinical and surgical variables as well as with postoperative outcome. Animals One hundred and twenty‐seven client‐owned dogs. Methods Dogs with pituitary corticotroph adenomas that underwent transsphenoidal hypophysectomy were retrospectively included. Plasma sodium and potassium concentrations were measured −2, +2, +8, +24, and +48 hours from hypophysectomy. Clinical (breed, age, body weight, skull type, urinary cortisol/creatinine ratio, percentage of suppression to dexamethasone) and surgical variables (duration of anesthesia and surgery, pituitary dimensions) were compared to the development of hypernatremia. Results Postoperative hypernatremia developed in 46.5% (57/127) of dogs and hyponatremia in 6.3% (8/127). Plasma sodium concentration increased after surgery and peaked at 8 hours after surgery, normalizing after 24 to 48 hours. Plasma potassium concentration increased without exceeding the reference limit. No significant associations were found between clinical and surgical variables and hypernatremia, or between hypernatremia and postoperative death, long‐term survival or recurrence. Surgery time was significantly longer in dogs that developed persistent diabetes insipidus ( P = .02) and persistent diabetes insipidus occurred more frequently in dogs with enlarged pituitary glands ( P = .01). Conclusion and Clinical Importance Hypernatremia remains a frequent postoperative complication after transsphenoidal hypophysectomy but did not appear to have an impact on postoperative outcome. No predisposing factor to postoperative hypernatremia was identified. Variations in plasma potassium concentrations do not seem to influence postoperative outcome.

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“…Anti-AVP antibody (rabbit anti-human vasopressin, Biomeda Corp.) was used [22]. After staining, AVP-immunopositive cells were counted in the SON and PVN of the hypothalamus in each section, and the largest number of immunopositive cells was adopted.…”

Section: Animalsmentioning

confidence: 99%

Relationship between Arginine Vasopressin and High Signal Intensity in the Pituitary Posterior Lobe on T1-Weighted MR Images in Dogs

Teshima

Hara

Masuda

et al. 2008

The Journal of Veterinary Medical Science

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ABSTRACT. The posterior lobe of the pituitary gland (PL) normally shows characteristic high signal intensity (SI) on T1-weighted MR images (T1WI) in humans. The high SI is thought to represent storage of arginine vasopressin (AVP) in the PL. Normal dogs also show a high SI on T1WIs, but the origin is unclear. In the present study, we investigated whether the high SI in the PL on T1WIs in normal dogs is caused by AVP. We examined the SI in the PL on T1WIs, plasma AVP concentrations and plasma osmolality in normal dogs after excessive AVP secretion was induced by hypertonic saline overload. In addition, functional changes in the supraoptic nucleus and paraventricular nucleus of the hypothalamus under AVP secretion-stimulated conditions were examined immunohistologically. Under hypertonic saline overload, plasma osmolality and plasma AVP concentrations gradually increased, while the SI of the PL gradually decreased. This suggests that AVP secretion was stimulated by elevated osmolality. Moreover, there was a significant negative correlation between plasma AVP concentrations and the SI ratio of the PL. An immunohistochemical study of the hypothalamus nucleus revealed that AVP-immunopositive cells significantly increased in the hypertonic saline loaded dogs. We concluded that the high SI in the PL in T1WIs in normal dogs was caused by AVP stored at the site, and examination of the SI in the PL using MRI is useful for diagnosis of abnormal pituitary glands. KEY WORDS: arginine vasopressin, canine, MRI, pituitary, signal intensity.J. Vet. Med. Sci. 70 (7): [693][694][695][696][697][698][699] 2008 Magnetic Resonance Imaging (MRI) provides detailed anatomic information and is a useful diagnostic modality for a variety of diseases in human and veterinary clinical medicine. In particular, the utility of the MRI has been recognized in examinations of the central nervous system. It has been used not only to examine morphological changes in the hypothalamic-neurohypophyseal (HNS) system, but also to evaluate function by examining signal intensity in images [3]. For these reasons, the MRI is the first-choice modality for evaluation of HNS disease.The posterior lobe of the normal pituitary shows characteristically high signal intensity (SI) in T1-weighted images (T1WI) at two months after birth or later in humans, which differs from the anterior lobe of the pituitary [2,6,20]. In addition, the characteristically high SI is markedly decreased by depletion of arginine vasopressin (AVP) due to disorders such as central diabetes insipidus [8,[17][18][19]. On the basis of this change in T1WIs, the MRI is used for diagnosis of diabetes insipidus [16], ectopic posterior lobe [9,24] and depleted posterior lobe of the pituitary by continuous excessive AVP secretion due to diabetes mellitus [5]. Moreover, the presence and localization of the characteristically high SI (so-called "pituitary flush") can be helpful in diagnosing microadenoma in dogs with pituitary-dependent hyperadrenocorticism without obviously enlarged pituitaries [23]...

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Functional and Morphological Changes in the Hypothalamus-Pituitary Posterior Lobe System after Hypophysectomy in the Dog

Cited by 5 publications

References 25 publications

<p>Transsphenoidal Surgery in Canines: Safety, Efficacy and Patient Selection</p>

<p>Transsphenoidal Surgery in Canines: Safety, Efficacy and Patient Selection</p>

Plasma sodium and potassium concentrations after hypophysectomy in dogs with corticotroph adenomas

Relationship between Arginine Vasopressin and High Signal Intensity in the Pituitary Posterior Lobe on T1-Weighted MR Images in Dogs

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