A 7-year-old mixed breed spayed bitch (body weight: 10.6 kg) was presented with a history of intermittent episodes of seizures and untreated limb fracture. Appetite loss, nervousness, lateral recumbency, fasciculations, ataxia and poor nutritional condition were found. Venous blood gas analysis highlighted normal acid-base balance and severe low ionized calcium (0.58 mEq/L [range 1.13-1.32 mEq/L]). Marked total hypocalcaemia (6.4 mg/dL [range 8-10] or 1.6 mM [range: 2-2.5]) associated with hyperphosphoraemia (9.3 mg/dl [range 3.5-6.5 mg/dl]) displayed inverted ratio between minerals. ECG showed sinus arrhythmias. Circulating levels of Mg and Cu were within physiological range (1.97 mg/dl and 128 μg/dl respectively) and effects from interactions were excluded. Oral administration of calcitriol at 40 ng/kg/day led to clinical improvement within 48 hours, but circulating iCa levels were still below the lower limit of the reference range. Baseline levels of circulating parathormone (PTH) were 3 pg/ml, along with normal values of circulating vitamin D. Primary hypoparathyroidism was diagnosed as a chronic underlying condition triggered by pelvic fracture.
Keywords: hypocalcaemia; ionized Ca; parathormone; seizure.
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