Primary hyperparathyroidism in a 17‐year‐oldArab ×WelshCob pony mare with a functional parathyroid adenoma

Abstract

Summary Primary hyperparathyroidism was identified in a 17‐year‐old Arab × Welsh Pony mare that experienced weight loss for 6 months and was presented with mild facial asymmetry, right forelimb lameness and weight shifting amongst all limbs. Osteodystrophia fibrosa was demonstrated on radiographic examination of the head and there was radiographic evidence of osteopenia of the appendicular skeleton. The horse had persistent hypercalcaemia (4.0 mmol/l), hypophosphataemia (0.59 mmol/l) and an increased concentration of circulating parathyroid hormone (1401 pg/ml). On scintigraphic examination, a subjective focal increase in uptake of 99mtechnetium‐sestamibi was identified in the right thyroid gland and at the thoracic inlet in delayed images. Surgical exploration of the thyroid region was unrewarding, whereas surgery at the thoracic inlet was not undertaken. One year later, the horse developed a pathological fracture of the third metacarpal bone and was subjected to euthanasia. At post mortem examination, a parathyroid adenoma was found at the level of the thoracic inlet adjacent to the trachea. Gross and histological examination also confirmed severe osteodystrophia fibrosa and osteopenia.

Endocrine tumours in equids

“…; Cottle et al . ) and reported cases have been consistent with parathyroid adenomas. To the authors’ knowledge, parathyroid carcinomas have not been reported in horses.…”

“…; Cottle et al . ). Laboratory findings in these patients are hypercalcaemia along with high serum parathyroid hormone (PTH) concentrations, with PTH related peptide (PTHrP) levels within normal limits, and hypophosphataemia (Toribio ; Tomlinson et al .…”

“…; Cottle et al . ), causing an excessive and autonomous secretion of parathyroid hormone. Parathyroid glands are difficult to identify during post‐mortem examinations and nonfunctional tumours in clinically normal horses should not be discarded.…”

Diagnosis and treatment of confirmed and suspected primary hyperparathyroidism in equids: 17 cases (1999–2016)

“…An additional case report of PHPT exists in which the horse showed increased radiopharmaceutical uptake at both the thyroid and the thoracic inlet, and surgical exploration of the thyroid region was unrewarding. Post‐mortem examination later revealed a parathyroid adenoma at the thoracic inlet . The reasons for the surgical failures in this study could include the presence of multi‐gland disease, misidentification of abnormal tissue on ultrasonography or scintigraphy and misidentification of adenomatous tissue at surgery.…”

“…Hyperparathyroidism is characterised by inappropriately high production of parathyroid hormone (PTH) by the chief cells of the parathyroid gland and subsequent derangements in calcium and phosphorous homoeostasis [2]. Clinical signs include anorexia, weight loss, osteodystrophia fibrosa of the facial bones, osteopenia and lameness [1,[3][4][5][6][7]. Both primary [1,[3][4][5][6][7] and secondary [8,9] hyperparathyroidism have been reported in equids.…”