Primary hyperparathyroidism in dogs: 21 cases (1976-1986)

Case records from 21 dogs with hypercalcemia and hyperparathyroidism were evaluated. The dogs were greater than or equal to 7 years old, and 6 were Keeshonds. The most common clinical signs were polydipsia/polyuria, listlessness, and muscle weakness. The serum calcium concentrations were 12.1 to 19.6 mg/dl. Serum phosphorus concentrations were low in 5 dogs, within the reference range in 13 dogs, and high in 3 dogs that also had high concentrations of BUN. Twenty dogs had a parathyroid adenoma, and 1 had a parathyroid carcinoma. Nineteen dogs had their parathyroid tumor surgically removed. Within 5 days of tumor removal, 11 of the 19 dogs became hypocalcemic and the remaining 8, normocalcemic. Nine of the 11 hypocalcemic dogs developed clinical signs. Iatrogenic hypercalcemia was induced in 7 of 16 dogs treated orally with calcium carbonate plus vitamin D. Only 1 of 19 dogs that had their parathyroid tumor excised died in hypocalcemic tetany. Two additional dogs died within 2 weeks of surgery, one because of pancreatitis, the other due to renal failure. Eight dogs died 9 to 37 months after surgery of unrelated problems. Eight dogs were alive for at least 7 to 28 months after surgery.

Radioimmunoassay for parathyroid hormone in equids

Radioimmunoassay for parathyroid hormone (PTH) in equids was performed on blood samples from healthy equids and equids with hypercalcemia and hypophosphatemia. The assay was validated for equine carboxy-terminal PTH. Manipulation of serum ionized Ca in healthy equids by infusing Na2 EDTA and CaCl2 produced an expected increase and decrease, respectively, in measurable immunoreactive PTH. Intra-assay and interassay coefficients of variation were 2.6% and 11.7%, respectively. The range of PTH valves for healthy mature horse mares and geldings maintained on pasture was less than 0.27 ng/ml to 0.92 ng/ml and for horse colts fed grain was 0.61 to 1.25 ng/ml. Serum PTH values were measured on 2 equine patients with hypercalcemia, 1 pony with primary hyperparathyroidism and 1 horse with pseudohyperparathyroidism. Both patients had increased serum PTH values.

Primary hyperparathyroidism in a dog: biochemical, bone histomorphometric, and pathologic findings

An adult Keeshond had clinical signs associated with hypercalcemia, including inappetence, polyuria, polydipsia, and vomiting. Blood biochemical findings and urinary clearance studies were consistent with a diagnosis of primary hyperparathyroidism. Histomorphometric analysis of trabecular bone in an iliac crest biopsy indicated increased bone remodeling activity. Surgical exploration of the neck revealed an oval mass, which was removed by blunt dissection. Histologic diagnosis was parathyroid gland adenoma. The dog died because of renal failure on the eighth postoperative day. This report defines primary hyperparathyroidism in the dog, thus facilitating diagnosis for the veterinary clinician.

Canine primary hyperparathyroidism and its association with urolithiasis

Primary hyperparathyroidism results from autonomous secretion of parathyroid hormone by a single or multiple parathyroid glands. Clinical signs result from various combinations of hypercalcemia, hypercalcemic nephropathy, urolithiasis, or mobilization of calcium and phosphorus from bone. Following parathyroidectomy, the prognosis for dogs with primary hyperparathyroidism is good if the disorder is diagnosed before renal disease is advanced.

Canine calcium phosphate uroliths

Uroliths composed primarily of calcium phosphate are identified in approximately 3 per cent of canine stone patients. Predisposing factors to the formation of calcium phosphate uroliths include elevated urine pH, hypercalciuria, and the presence of crystallization inhibitors and promoters. Medical therapy of patients forming calcium phosphate uroliths should initially be directed at removing factors contributing to urine supersaturation with calcium phosphate.

Equine blood serum calcium and phosphorus concentrations in progressive nutritional hyperparathyroidism

Weekly blood serum samples from 20 yearling horses, divided into equal groups, receiving diets with total calcium to inorganic phosphorus ratios of 1,5/1 and 0,2/1, were analysed for calcium and phosphorus concentrations. This was done over a continuous 23 week period, divided into 2 sub-periods of 16 and 7 weeks each. During the first period complete diets were provided ad lib but were restricted during the second period to accentuate any effects of calcium deficiency and phosphorus excess. Falling calcium levels and rising phosphorus levels during period 1 and a reverse trend during period 2 indicated that this method can be used to detect progressive nutritional hyperparathyroidism in individual horses when a series of profiles are analysed over a period of time.

Syncytial cells in canine parathyroid glands

Multinucleated syncytial cells consisting of clusters of closely apposed, darkly staining nuclei and densely eosinophilic cytoplasm were present in parathyroid glands from 25 of 36 dogs (69%). They were most often located either peripherally in the parathyroid gland or adjacent to blood vessels. The numbers of nuclei per syncytial cell ranged from two to greater than 30. Syncytial cells had degenerative changes as suggested by vacuolated mitochondria, dilated rough endoplasmic reticulum, irregular nuclear outlines, and condensed nuclear chromatin. These ultrastructural changes contrasted sharply with adjacent chief cells that had well-preserved organelles. The presence of desmosomes and fragments of cell membranes between nuclei suggested that syncytial cells were derived from fusion of adjacent chief cells rather than nuclear division without cytokinesis. Syncytial cells were present in normal, hyperplastic, and inactive parathyroid glands from dogs. There were no significant correlations between the presence of multinucleated cells and age of dog, parathyroid histology, and changes in the concentrations of serum calcium, phosphorus, creatinine, or plasma parathyroid hormone. Syncytial cells occurred frequently in canine parathyroid glands regardless of the state of activity of the gland or the concentration of plasma parathyroid hormone or serum calcium.

Primary hyperparathyroidism in German shepherd dogs: a disorder of probable genetic origin

Primary hyperparathyroidism was diagnosed in two German shepherd pups from a litter of four females. Clinical signs were apparent by two weeks of age and included stunted growth, muscular weakness, and polydipsia/polyuria. Radiography revealed diffuse reduction in bone density. Both pups had marked hypercalcemia, hypophosphatemia, increased plasma immunoreactive parathyroid hormone concentrations and increased fractional clearance of inorganic phosphate in the urine. Intravenous infusion of one affected pup with calcium gluconate failed to suppress the plasma concentration of immunoreactive parathyroid hormone, suggesting autonomous secretion of parathyroid hormone. Necropsy of the other pup at eight weeks of age revealed diffuse hyperplasia of parathyroid chief cells, nodular hyperplasia of thyroid C-cells, skeletal alterations consistent with fibrous osteodystrophy, hypercalcemic nephropathy, and extensive mineralization of the lungs and gastric mucosa. The dam and sire were half sibs. One male pup from a previous litter of six had developed similar clinical signs and radiographic lesions, suggesting autosomal recessive inheritance. This is the first report of hereditary primary hyperparathyroidism in domestic animals, a disease which may be analogous to hereditary neonatal primary hyperparathyroidism in children.

Morphologic characteristics of the parathyroid and thyroid glands and serum immunoreactive parathyroid hormone in dogs with pseudohyperparathyroidism

Hypercalcemia, normo- or hypophosphatemia, and increased urinary calcium clearance were observed in 8 dogs with malignant disease consisting of lymphosarcoma (n = 4), lymphogenous leukemia with bone involvement (n = 2), or carcinoma arising in the perianal region (n = 2). Parathyroid glands from these dogs had a normal or atrophic microscopic appearance. Ultrastructurally, the chief cells of the parathyroid glands had small cytoplasmic areas devoid of secretory granules and containing few organelles associated with hormonal synthesis, which is indicative of an inactive phase of the secretory cycle. In relationship to total serum calcium, serum canine immunoreactive parathyroid hormone was moderately increased in 3 dogs whose parathyroid glands had morphologic characteristics of inactivity. As a result of prolonged hypercalcemia, the thyroid glands contained prominent areas of parafollicular cell hyperplasia. The ultrastructure of a typical hyperplastic parafollicular cells was characterized by a large cytoplasmic area filled with numerous secretory granules and moderate numbers of organelles associated with hormonal synthesis. The results of this study indicate that some nonendocrine malignant neoplasms of dogs may be capable of secreting a hypercalcemia substance immunologically indistinguishable from parathyroid hormone. In the absence of neoplastic involvement of bone, the canine disease has many similarities to pseudohyperparathyroidism.

Juvenile rickets and hyperparathyroidism in the Arctic fox

Three of seven Arctic fox kits, Alopex lagopus, trapped on St. Paul Island, Alaska, had evidence of rickets and hyperparathyroidism. Radiographic, morphologic and histologic examination confirmed the diagnosis. The disease was presumed to be a juvenile-onset disease due to calcium-deficient intake following weaning. The possibility of insufficient exposure to sunlight could not be determined. No other abnormalities (e.g., genitourinary) were found. Skeletal involvement was quite varied. All growth plates exhibited columnar hyperplasia compatible with rickets, while the metaphyses showed decreased trabeculation and cortical thinning compatible with osteodystrophia fibrosa. One fox had bilateral metaphyseal fractures through this osteodystrophic bone.

Regulatory hyperparathyroidism in a pig breed with vitamin D dependency rickets

A radioimmunoassay for porcine parathyroid hormone has been developed and applied to measure immunoreactive parathyroid hormone (PTH) in plasma of pigs with hereditary vitamin D dependency rickets (VDDR) (pseudovitamin D deficiency rickets). Levels of 25-hydroxycholecalciferol (25-(OH)-D3) in plasma were measured by a protein binding assay. Both plasma concentrations of PTH and 25-(OH)-D3 showed an approximately 4-fold increase compared to normal pigs. PTH levels increased with duration of the disease. Daily dosing of the animals with 1--4 micrograms of 1,25-dihydroxycholecalciferol (1,25-(OH)2-D3) reduced PTH concentrations and resulted in clinical healing. Iv administration of 10 micrograms of 25-(OH)-D3/day did not alter PTH concentrations nor the clinical symptoms. The results suggest that these animals suffer from regulatory hyperparathyroidism. The metabolic defect could be due to a failure of the kidney to convert 25-(OH)-D3 to 1,25-(OH)2-D3.

Effects of hyperparathyroidism and dietary calcium supplementation on bone healing

Effects of nutritional secondary hyperparathyroidism and dietary calcium supplementation on bone healing were determined. Groups (n = 4) of 5 mature male dogs each were fed the following diets: group 1, control diet (0.48% Ca, 0.43% P); group 2, test diet (0.12% Ca, 1.14% P): group 3, control diet plus calcium; group 4, test diet plus calcium. The dietary calcium supplementation was calcium gluconate. Lesions were induced in the right tibial cortex by trephinization. Within the time limitations of this study, it was determined that nutritional secondary hyperparathyroidism does not inhibit bone healing and that dietary calcium supplementation does not aid bone healing.

Primary hyperparathyroidism in a dog

A 6-year-old male Standard Poodle had hypercalcemia, hypophosphatemia, and a urinary concentrating defect. A parathyroid adenoma involving the left caudal parathyroid gland was surgically removed. Transient hypocalcemia followed, which resolved without treatment. A renal biopsy did not demonstrate renal parenchymal mineral deposition. Urinary concentrating ability returned after surgery.

Pseudohyperparathyroidism associated with perirectal adenocarcinomas in elderly female dogs

In 8 elderly female dogs a syndrome of hypercalcaemia and hypophosphataemia was found in association with a perirectal adenocarcinoma. Following removal of the tumour the hypercalcaemia resolved within two days in four of the five operated animals.