Veterinary Clinics of North America - Exotic Animal Practice最新文献

Regardless of species, calcium, vitamin D, and parathyroid hormone physiology are intricately linked. However, there are many unique differences between taxa that may affect husbandry recommendations, common disease processes, and effective treatment. This article aims to provide a basic overview of calcium metabolism and physiology then specifically delve into unique attributes of calcium homeostasis in common zoologic companion animal species.

Diagnostic imaging can provide essential evidence supporting the diagnosis of endocrine diseases in exotic companion animals. The specific modality chosen depends on species, specific disease process/organ affected, equipment availability, and often, cost to the owner. While radiography is widely available in veterinary practices, the sensitivity for visualization of endocrine organs is low. Therefore, ultrasonography, computed tomography, or MRI may be preferred. Other specialized imaging modalities are useful for specific disease processes, such as nuclear scintigraphy and PET. This article compiles current evidence for diagnostic imaging of the endocrine system in exotic animals, organized by imaging modality, species, and disease process.

Birds (class Aves) have 1.5 to 2 times higher blood glucose concentrations than mammals of comparable sizes. The reasons for this have been studied and are believed to be multifactorial. There is low expression of insulin receptors, decreased sensitivity of the pancreatic β-cells to glucose, an absent or dysfunctional glucose transporter type 4 pathway, and increased blood glucagon concentrations. Glucagon and somatostatin appear to play a greater role than insulin in glucose homeostasis in birds. Severe hyperglycemia in birds can be attributed to diabetes mellitus, necessitating therapy to prevent short-term and long-term deleterious effects.

Across all vertebrates, the anatomy of the hypothalamus and mechanisms underlying its development are highly conserved, whereas the pituitary is highly specialized structurally with considerable differences amongst classes. In birds and reptiles, the hypothalamus controls the pituitary gland through nerve impulses and the secretion of neurohormones, resulting in several hypothalamic-pituitary axes: the hypothalamic-pituitary-thyroid axis, the hypothalamic-pituitary-adrenal axis, and the hypothalamic-pituitary-gonadal axis. This article provides a foundational knowledge on the physiologic function of the hypothalamus and pituitary in birds and reptiles, and their effects on behavior, homeostasis, and disease.

The paraphyletic group referred to as fishes represents several extant and extinct classes that demonstrate the greatest diversity and abundance of any of the vertebrates on the Earth. Anatomically and physiologically, the systems of fish are comparable to those of other vertebrates and the thyroid and hypothalamic-pituitary-thyroid (HPT) axis are no exceptions. This article reviews the current literature on thyroid endocrinology of elasmobranch and teleost fishes with an emphasis on relevance to clinical management and highlights some of the anatomic and physiologic differences of the HPT axis in fishes.

Adrenal gland disease has been described as a rare disease in pet rabbits and rodents. Hyperadrenocorticism with excessive secretion of corticosteroids is most commonly observed in guinea pigs and hamsters, with dermatologic signs similar to those seen in dogs. Diagnosis is based on clinical signs, diagnostic imaging such as abdominal ultrasound, and determination of the blood hormone concentrations. In guinea pigs, an adrenocorticotrophic hormone stimulation test with the measurement of salivary cortisol or corticosterone concentrations is recommended. The recommended treatment of adrenal disease in guinea pigs and hamsters is oral administration of trilostane or ketoconazole; surgical treatment is also possible.

Endocrine diagnostics currently depend on the ability to measure low and high concentrations of diagnostic hormones using immunoassays. This often is challenging in species other than humans, dogs, cats, and horses due to lack of validated assays and reference intervals. There are strategies to approach endocrine testing in zoo, wildlife, and zoologic companion animals but caution is needed in interpreting results. Newer techniques such as liquid chromatography-tandem mass spectrometry (LC-MS/MS) may be more useful for all species, although technical hurdles remain for this method too.

Research in reproductive management of reptiles has focused on developing and investigating feasible methods that can be used in clinical practice and laboratory settings, including sexing in monomorphic species and methods of artificial insemination in endangered reptile species. In captive pet reptile species, research is focused on hormonal regulation of reproductive activity. Gonadotropin-releasing hormone (GnRH) agonist implants may temporarily suppress reproductive endocrine system (eg, circulating concentrations of estrogens and progesterone) in female green iguanas but did not influence male iguana behavior and plasma testosterone levels. Additionally, it did not suppress reproductive activity of females of other lizard species (eg, leopard geckos).

Cystic ovarian disease is the most common reproductive tract disorder in female guinea pigs, and concurrent uterine pathology may also be present. Nonspecific clinical signs include decreased appetite, lethargy, hunched posture, weight gain, palpable mass(es) in the midabdomen, and progressive abdominal distension. Additionally, bilateral, nonpruritic alopecia of the flank and ventral abdomen; hyperkeratosis, crusting, and/or hyperpigmentation of nipples; clitoral hypertrophy; reduced fertility; and behavioral changes may also be appreciated. Confirmation of disease is most often made with abdominal ultrasound but may also occur during exploratory abdominal surgery. Recommended treatment is surgical management with ovariohysterectomy or ovariectomy.