Evaluation of Precision and Establishment of Reference Ranges for Plasma Thyroxine using a Point-of-Care Analyzer in Healthy Guinea Pigs (Cavia porcellus)

Tomographic and ultrasound evaluation of the thyroid gland in pet guinea pigs

There has been increasing interest in the literature on primary thyroid diseases in guinea pigs, which are believed to be underdiagnosed. This study describes the size and characteristics of the thyroid gland on ultrasound (US) and CT examinations in the guinea pig (Cavia porcellus) without evidence of thyroid pathology and examines the possible use of US as a routine examination for thyroid diseases. This prospective and anatomical study included 20 guinea pigs that underwent CT for dental pathologies and US for thyroid gland (TG) examination. Based on US and CT images, this study evaluated the thyroid lobe dimensions (length, height, and width) and shape. Echogenicity and homogeneity were assessed on US images, and attenuation values (HU) and homogeneity were evaluated on CT images. All animals underwent CT and US examinations under anesthesia. Thyroid lobes appeared more frequently as fusiform on CT (65%) and oval on US scans (67.5%). The attenuation values on CT scans were homogeneous. On the US scans, the TG was more frequently hypoechoic. No statistically significant differences were found between the size of the right and left thyroid lobes, both with CT and US. A statistically significant difference was found between the length values on CT and US. The US and CT thyroid gland dimensions, shape, and appearance were described. Both CT and US are useful techniques for evaluating the TG in guinea pigs.

Endocrine Diagnostics: Principles and Applications

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.

Thyroid Disease in Rabbits and Rodents

While thyroid disease is generally uncommon in rabbits and rodents, it is most frequently diagnosed in guinea pigs. Particularly, hyperthyroidism and thyroid neoplasms are diagnosed regularly in this species, while thyroid neoplasia is the most common thyroid disorder found in other rodents. Thyroid disease appears to be rare in rabbits, though modalities to reliably diagnose different disorders like hypothyroidism are currently lacking.

Endocrine Diagnostics for Exotic Animals

Endocrine disease in exotic species is less common than in small animals. Nevertheless, the diagnostic principles used in small animals can be adapted to evaluate endocrine disease in many of the exotic species although species-specific aspects need to be considered. This article covers important diseases such as thyroid dysfunction in reptiles and birds, hyperthyroidism in guinea pigs, and hyperadrenocorticism in ferrets. Glucose metabolism in neoplasms affecting normal physiology, such as insulinoma in ferrets and gastric neuroendocrine carcinoma in bearded dragons, is discussed. Calcium abnormalities, including metabolic bone disease in reptiles and hypocalcemia in birds, are also covered.

Updates on Thyroid Disease in Rabbits and Guinea Pigs

Hyperthyroidism seems to be a rare, but likely underdiagnosed disease of guinea pigs (Cavia porcellus) and rabbits (Oryctolagus cuniculus). Diagnosis is confounded by nonspecific clinical signs, lack of validated assays, and species-specific reference intervals. With increasing English-language publications on the topic, naturally occurring thyroid disease is likely to be increasingly diagnosed in exotic small mammals. The most consistently observed clinical signs include weight loss with or without a change in appetite and a palpable cervical mass. Diagnosis is supported by elevated blood thyroxine concentrations. Treatment may include thyreostatic agents, radioactive iodine, or surgical thyroidectomy.

Advances in Exotic Animal Clinical Pathology

Over the last 10 years, exotic animal clinical pathology has been evolving, improving health assessment in avian, mammal, fish, reptile, and amphibian patients. These advances are reviewed in this article. Species-specific reference intervals for blood parameters are becoming more available (eg, for ionized calcium, endocrine panels, and vitamin D plasmatic concentrations). In addition, new technologies are being developed to facilitate targeted metabolite detection and result acquisition by veterinarians. Novel techniques, biomarkers, and clinical changes related to disease have been described in avian, mammal, fish, reptile and amphibian species. The use of mobile applications may also be helpful.

Case Report of a Satin Guinea Pig with Fibrous Osteodystrophy That Resembles Human Pseudohypoparathyroidism

A case report of a 2-year-old female satin guinea pig with a history of dental overgrowth and lameness and radiological lesions of fibrous osteodystrophy is presented. The most relevant clinical findings were bone demineralization, high level of parathyroid hormone (PTH), normophosphatemia, normal ionized calcium, and low total thyroxine (tT4) with a normal renal function. Long-term treatment was based on teeth coronal reduction and maintaining a balanced diet. PTH measurement was performed with a kit suitable for rats to test 4 different paired samples of guinea pigs and resulted in similar results for each pair of measurements. Two kits routinely employed in dogs and cats failed in measuring PTH in guinea pig serum samples. The ionized calcium, PTH, and tT4 values, not previously reported in similar cases, were obtained. The determination of tT4 could be useful in the diagnosis of fibrous osteodystrophy in guinea pigs. The observed findings show similarity with human pseudohypoparathyroidism type Ia, a disease caused by an inactivating heterozygous mutation of the stimulatory G protein α subunit from the maternal genome that induces multiple hormone resistance and that courses with a syndrome called Albright hereditary osteodystrophy. Naturally occurring pseudohypoparathyroidism in animals has been reported previously only in a ferret.

Rodent Oncology: Diseases, Diagnostics, and Therapeutics

Cancer incidence in rodent species varies dramatically from a common occurrence in mice and rats to just a limited number of documented cases in chinchillas and degus. This article summarizes common tumors, both benign and malignant, that have been reported to occur in rodents. Outlined are clinical signs, diagnostics, and treatments that have been described for rodents presenting with specific neoplasms.

Thyroid diseases in rodent species

There are an abundance of studies of thyroid disease in rodents in a laboratory setting; however, research is limited in pet rodent populations. Validated reference intervals for thyroid testing are scarce, making interpretation of blood work difficult. Hyperthyroidism and hypothyroidism have been reported in multiple rodent species, with the most data available for guinea pigs. Thyroid neoplasia has been reported in the most common rodent species, although often as an incidental finding at necropsy. Further research is needed to determine frequencies of disease, methods of diagnosing, and treatment options with the best efficacy.

Hyperthyroidism and hyperparathyroidism in guinea pigs (Cavia porcellus)

Abnormal conditions of the thyroid and parathyroid in the guinea pig appear in the English-language scientific literature on an emerging basis. Although true descriptions of abnormal thyroid and parathyroid anatomy or morphology are not new findings, the clinical condition of abnormal thyroid or parathyroid function seems to be a more common observation by clinicians in recent years. This article is an overview of general clinical conditions and adequate diagnosis, and offers treatment options.