A 65 year old lady hospitalized for cervical spondylosis was found to have serum calcium of 12.5mg%. Her haematocrit and KFT is normal with phosphate of 2.3mg/dl. Which is the first investigation to be done in the patient?

In an Asymptomatic patient with hypercalcemia, the leading cause happens to be hyperparathyroidism. PTH causes urinary loss of Phosphate, which explains low phosphate in the patient. (Normal phosphate=2.5-4.5mEq/dl) PTH assay is the first investigation to be done in this case. Most patients of hyperparathyroidism are initially asymptomatic and later develop nephrolithiasis, peptic ulceration, constipation and altered mental status. In symptomatic hypercalcemia, cancer is the leading cause. Hence work up for squamous cell cancer of lung and breast cancer should be done. Choice C is done for multiple myeloma. It is ruled out since phosphate is normal in Multiple myeloma. Choice D is ruled out as hypervitaminosis is a rare cause and there is no history of taking any health supplements. Also both calcium and phosphate are elevated in hypervitaminosis D.