ABSTRACT
We describe the clinical presentation, investigation and management of an eventually fatal case of hypercalcemic crisis due to primary hyperparathyridism (PHPT). A 60 year-old lady with history of urolithiasis presented with worsening generalized bone pain, spinal scoliosis and a limp. Laboratory data showed hypercalcemia and raised alkaline phosphatase. Left hip x-ray revealed a subcapital femoral neck fracture. Intact parathyroid hormone was elevated, 187.6 pmol/L (1.6 – 6.9) and ultrasound showed an enlarged right parathyroid gland. Despite initial reduction of serum calcium with saline infusion and multiple doses of intravenous pamidronate, her calcium increased to 4.14 mmol/L a week following application of Buck’s traction for persistent left hip pain. She succumbed eventually with serum calcium peaking at 6.28 mmol/L despite multiple therapeutic interventions.
ABSTRACT
<p><b>INTRODUCTION</b>In a patient with hyperthyroidism, the detection of elevated thyroid hormone concentration with measurable thyroid-stimulating hormone (TSH) value poses considerable diagnostic difficulties.</p><p><b>CLINICAL PICTURE</b>This 38-year-old lady presented with clinical features of thyrotoxicosis. Her serum free thyroxine concentrations were unequivocally elevated [45 to 82 pmol/L (reference interval, 10 to 20 pmol/L)] but the serum TSH values were persistently within the reference interval [0.49 to 2.48 mIU/L (reference interval, 0.45 to 4.5 mIU/L)].</p><p><b>TREATMENT</b>Investigations excluded a TSH-secreting pituitary adenoma and a thyroid hormone resistance state and confirmed false elevation in serum TSH concentration due to assay interference from heterophile antibodies. The patient was treated with carbimazole for 18 months.</p><p><b>OUTCOME</b>The heterophile antibody-mediated assay interference disappeared 10 months following the initiation of treatment with carbimazole, but returned when the patient relapsed. It disappeared again 2 months after the initiation of treatment.</p><p><b>CONCLUSIONS</b>Clinicians should be aware of the potential for interference in immunoassays, and suspect it whenever the test results seem inappropriate to the patient's clinical state. Misinterpretation of test values, arising as a result of assay interference, may lead to misdiagnosis, unnecessary and at times expensive investigations, delay in initiation of treatment and worst of all, the initiation of inappropriate treatment.</p>