Endocrine Abstracts

Introduction: Primary hyperparathyroidism (PHPT) is usually caused by a single hyperfunctioning parathyroid adenoma. Preoperative localization studies allow for minimally invasive surgical removal. We present a case of PHPT caused by a solitary adenoma that could not be localised pre-operatively and review existing and emerging localisation modalities.

Case report: A 65-year-old Chinese lady admitted for neck of femur fracture was found to have hypercalcaemia of 2.82 mmol/l (RI: 2.15–2.58 mmol/l) and PTH level of 16.2 pmol/l (RI: 0.8–6.8 pmol/l). History was unremarkable for renal impairment, drug related causes or malignancy. Her calcium/creatinine clearance ratio of 2.12% was suggestive of PHPT. Ultrasonography did not localize any hypoechoeic ovoid structures but showed multiple thyroid nodules. Fine needle aspiration cytology (FNAC) of the thyroid nodules was negative for malignancy. Dual tracer parathyroid scintigraphy did not reveal any sestamibi-avid or enlarged parathyroid lesion. A total thyroidectomy and exploratory parathyroidectomy subsequently revealed a right parathyroid adenoma embedded within the thyroid tissue.

Discussion: PHPT is accounted for by a solitary adenoma in 85–90% of all cases. Pre-operative localization techniques allows for minimally invasive surgery which reduces morbidity. Non-invasive modalities include ultrasonography, parathyroid scintigraphy, sestamibi-single photon emission computed tomography (SPECT), 4-dimensional CT, positron emission tomography and MRI, with scintigraphy being the most sensitive (scintigraphy 54–96%, 4D-CT 88%, SPECT 79%, ultrasonography 76%, MRI 43–71%). The sensitivity of scintigraphy is decreased in four-gland hyperplasia, double adenomas or concomitant thyroid disease. The results of scintigraphy can be enhanced by combination with SPECT or using dual tracer subtraction scans. Invasive techniques such as venous PTH sampling and selective arteriography are reserved for patients with recurrent or persistent hyperparathyroidism.

Conclusion: The pre-operative localisation of a solitary adenoma in PHPT remains a challenge despite new, emerging techniques.