What is the most likely cause of the hypercalcaemia?

A 55-year-old woman presented with a 3-week history of nausea and vomiting. Her only medical complaints were frequent dyspepsia, for which she was taking indigestion tablets, and asthma for which she was taking a salbutamol inhaler as required.

On examination, there was no evidence of lymphadenopathy, her chest was clear on auscultation and abdominal examination was normal.

Investigations (before and after taking omeprazole for 3 weeks):

beforeafternormal

erythrocyte sedimentation rate (mm/1st h)44<30

serum creatinine (µmol/L)17011060C110

serum corrected calcium (mmol/L)2.852.402.20C2.60

serum phosphate (mmol/L)1.90.8C1.4

serum angiotensin-converting enzyme (U/L)8525C82

plasma parathyroid hormone (pmol/L)0.44.40.9C5.4

What is the most likely cause of the hypercalcaemia?
A . milkCalkali syndrome
B . multiple myeloma
C . parathyroid hormone-related peptide-secreting malignancy
D . primary hyperparathyroidism
E . sarcoidosis