Endocrine Abstracts

Background: Successful parathyroidectomy depends on recognition and excision of all hyperfunctioning parathyroid glands.

The aim of the study was to estimate the diagnostic value of PTH concentration in the needle washout after fine-needle aspiration of foci suggestive of enlarged parathyroids in patients (pts) with hyperparathyroidism (HP).

Material and methods: Of 18 pts were studied (15 females, 3 males); 16 pts with primary HP (two recurrent), two with secondary HP, presenting with one or more intrathyroid foci on US. Serum PTH (PTH intact; Immulite 2000), total and ionized calcium, phosphate, alkaline phosphatase concentration were measured in all pts. ^99mTc-sestamibi parathyroid SPECT scintigraphy was performed. Dual tracer parathyroid ^99mTc-pertechnetate/^99mTc-sestamibi planar subtraction scintigraphy was recorded (X-Ring Mediso). Ultrasound guided (AU3 Partner, EsaoteBiomedica; 10 MHz) fine-needle biopsy was performed and sent for cytology. The needle (25G) was washed out with 125 μl (first biopsy) and 400 μl (second biopsy) of 0.9% saline. PTH concentrations (using the same PTH intact kit) in the washouts were measured. A positive cutoff value for PTH washout concentration was defined as superior to the PTH serum level. A preoperative ’map’ of the intrathyroid lesion was drawn. The drawing was placed above the patient’s head to serve as a guide for the surgeon performing open, focused surgery.

Results: All pts revealed parathyroid lesions. Hyperplasia was found in 11 pts (11/18; 61.1%), adenoma in 6 pts (6/18; 33.3%) and in one case (1/18; 5.6%) parathyroid cancer was suspected in pathology, but no metastatic foci have been diagnosed so far. All but one patient had elevated PTH washout concentrations-sensitivity 94.4%; positive predictive value (PPV) 100%. Positive scintigraphy (visible parathyroids) was found in 9 pts (9/18; 50.0%), positive cytology (detected parathyroid cells) was found in 12 pts (12/18; 66.7%).

Conclusions: An elevated PTH washout concentration identifies an intrathyroid focus as enlarged parathyroid gland with high PPV and high sensitivity. With this diagnostic technique, minimally invasive surgery can be implemented even in negative scintiscan cases, thus sparing the unchanged thyroid gland.