Which further finding is most likely to cast doubt upon this diagnosis?

A 61-year-old woman was found incidentally to have a raised serum calcium concentration. She was otherwise well. Her father had undergone a neck operation many years previously.

Investigations:

serum corrected calcium2.78 mmol/L (2.20C2.60)

plasma parathyroid hormone10.8 pmol/L (0.9C5.4)

Her general practitioner thought she had primary hyperparathyroidism.

Which further finding is most likely to cast doubt upon this diagnosis?
A . high serum 25-OH-cholecalciferol
B . low serum magnesium concentration
C . low urinary calcium excretion
D . normal parathyroid radioisotope scan (sestamibi scan)
E . normal serum phosphate concentration

View Answer

Answer: C