Corrected serum calcium < 11 mg/dL, and no evidence of symptomatic hypercalcemia; (corrected serum calcium is calculated by adding 0.8 mg/dL to the measured serum calcium for every 1 g/dL that the serum albumin falls below 4.0 g/dL) Serum calcium >11 mg/dL Subjects with serum calcium (corrected for albumin) ? 12 mg/dL Serum calcium > 8.5 and < 10.5 mg/dL Primary hyperparathyroidism (serum calcium [Ca] > 10.5 mg/dL and parathyroid hormone (PTH) > 72 pg/ml) Calcium (Ca) < 10.5 mg/dl Corrected serum calcium >= 14 mg/dl within 2 weeks of enrollment (despite appropriate measure such a short course of steroids, bisphosphonates, hydration, and calcitonin) Serum calcium =< 12.0 mg/dL Total serum calcium (corrected for serum albumin) >= 8.5 mg/dL or ionized calcium >= 3.8 mg/dL Serum calcium or albumin-adjusted serum calcium >= 2.0 mmol/L (8.0 mg/dL) and =< 2.9 mmol/L (11.5 mg/dL) Patients must have a serum calcium of >= 2.0 mmol/L (8.0 mg/dL) or albumin-adjusted serum calcium =< 2.9 mmol/L (11.5 mg/dL) within 30 days of registration; (Note: if patients are undergoing treatment for hypocalcemia and the serum calcium value at screening is > 8.0 mg/dl, then the patient will be eligible for this study) Corrected calcium >= 11.5 mg/dL within 2 weeks of randomization Serum calcium or albumin-adjusted serum calcium >= 2.0 mmol/L (8.0 mg/dL) and =< 2.9 mmol/L (11.5 mg/dL) Serum calcium =< 12.0 mg/dL Corrected serum calcium > 11.5 mg/dl within 2 weeks of enrollment Subjects with serum calcium (corrected for albumin) >= 12 mg/dL Serum calcium =< 12 mg/dl within 14 days of study entry Serum calcium (ionized or adjusted for albumin) < 8 mg/dl (1.75 mmol/L) or > 12.5 mg/dl (> 3.1 mmol/L) despite intervention to normalize levels Serum calcium < 11.6mg/dL Total serum calcium (corrected for serum albumin) >= 8.5 mg/dL or ionized calcium >= 3.8 mg/dL Corrected serum calcium level of > 10.5 mg/dL (serum corrected calcium = serum calcium + 0.8[4-serum albumin]) Uncontrolled hypercalcemia (defined as serum calcium > 14 mg/dL) Hypercalcemia: serum calcium > 11.5 mg/100 ml or Serum calcium or albumin-adjusted serum calcium >= 2.1 mmol/L (8.4 mg/dL) and =< 2.9 mmol/L (11.5 mg/dL) (reference range 8.5-10.8 mg/dL) Serum calcium (ionized or adjusted for albumin) < 7 mg/dl (1.75 mmol/L) or > 12.5 mg/dl (> 3.1 mmol/L) despite intervention to normalize levels Serum calcium (ionized or adjusted for albumin) < 7 mg/dl (1.75 mmol/L) or > 12.5 mg/dl (> 3.1 mmol/L) despite intervention to normalize levels Patient has symptomatic MM, as defined by any of the following:\r\n* Lytic lesions or pathologic fractures\r\n* Anemia (hemoglobin < 10 g/dL)\r\n* Hypercalcemia (corrected serum calcium > 11.5 mg/dL)\r\n* Renal insufficiency (creatinine > 1.5 mg/dL)\r\n* Other: symptomatic hyperviscosity, amyloidosis Calcium < 10.1 mg/dL (corrected to serum albumin) Baseline serum calcium < 8.4 mg/dL (calcium supplementation may be given to restore the serum calcium above this level prior to study entry) Screening serum calcium levels < 2.20 mmol/L [8.8 mg/dL] (after correction for serum\n albumin Hypercalcemia, defined as a calcium of > 11 mg/dL (C) Calcium elevation (serum calcium >11.5 mg/dl )(> 2.65 mmol/L) Corrected serum calcium >13.5 mg/dL (> 3.4 mmol/L) CTCAE version (v)4.0 grade 3-4 electrolyte abnormalities:\r\n* Calcium < 7 mg/dl or > 12.5 mg/dl;\r\n* Glucose < 40 mg/dl or > 250 mg/dl;\r\n* Magnesium < 0.9 mg/dl or > 3 mg/dl;\r\n* Potassium < 3 mmol/L or > 6 mmol/L;\r\n* Sodium < 130 mmol/L or > 155 mmol/L Corrected serum calcium superior to 14 mg per dL (superior to 3.5 mmol per L). Absence of hypercalcemia attributed to the plasma cell disorder*: calcium (Ca) < 10.5 mg/dl or =< 2.5 mmol/L\r\n* To be determined based on clinical and laboratory assessment by the primary oncologist Serum calcium =< 12.0 mg/dL Serum calcium or albumin-adjusted serum calcium >= 2.0 mmol/L (8.0 mg/dL) and =< 2.9 mmol/L (11.5 mg/dL) Hypercalcemia: serum calcium > 0.25 mmol/L (> 1 mg/dL) higher than the upper limit of normal or > 2.75 mmol/L (> 11 mg/dL) Serum phosphate levels >= 2.5 mg/dL or >= 0.8 mmol/L Serum calcium =< 12.0 mg/dL Calcium < 10.1 mg/dL (corrected to serum albumin) Serum calcium =< 12.0 mg/dL Patients with hypercalcemia (blood levels greater than 11.5 mg/dL) and/or abnormally high vitamin D levels (in patients with kidney disease, blood calcium levels must be 9.5 mg/dL or lower before starting paricalcitol) Serum calcium or albumin-adjusted serum calcium >= 2.0 mmol/L (8.0 mg/dL) and =< 2.9 mmol/L (11.5 mg/dL) Patient must have a calcium phosphate product (CPP) =< 4.0 mmol^2/L^2 or 50 mg^2/dL^2 Serum calcium =< 12.0 mg/dL Serum calcium =< 12.0 mg/dL Serum calcium =< 12.0 mg/dL For Cohort C only: Subjects must have a calcium phosphate product (CPP) of <4.4 mmol^2/L^2 (55 mg^2/dL^2) if they are to continue treatment with GSK1120212 Corrected calcium =< 10 mg/dL Serum calcium or albumin-adjusted serum calcium ? 2.0 mmol/L (8.0 mg/dL) and ? 2.9 mmol/L (11.5 mg/dL) Corrected calcium ? 11.5 mg/dL Serum calcium =< 12.0 mg/dL Corrected serum calcium > 14 mg/dL Serum calcium below the CTCAE grade 1 upper limit (11.5 mg/dL or 2.9 mmol/L); in cases where the serum calcium is below the normal range, the calcium adjusted for albumin is calculated and substituted for the measured value Subjects with serum calcium (corrected for albumin) ? 12 mg/dL. Myeloma-related organ dysfunction (at least one of the following) [C] Calcium elevation in the blood (serum calcium >10.5 mg/dl or upper limit of normal) [R] Renal insufficiency (serum creatinine >2 mg/dl) [A] Anemia (hemoglobin <10 g/dl or 2 g < laboratory normal) [B] Lytic bone lesions or osteoporosis AND have measurable disease by protein electrophoresis analyses as defined by the following: Be diagnosed with PHPT (inappropriate PTH level in the setting of a high or high-normal serum calcium level greater than or equal to 10.0 mg/dL). Patients with a calcium level greater than 13mg/dL. Corrected serum calcium less than or equal to 10.5 mg/dL Corrected calcium > 10.6 mg/dL Preoperative serum calcium levels >= 10.9 mg/dL Corrected serum calcium level less than or equal to 10.5 mg/dL Serum calcium <9.8 mg/dL Serum calcium or albumin-adjusted serum calcium 2.0 mmol/L (8.0 mg/dL) and 2.9 mmol/L (11.5 mg/dL) Serum calcium or albumin adjusted >= 8.0 mg/dL and =< 11.5 mg/dL Hypocalcemia (serum calcium or albumin adjusted calcium < 8.0 mg/dL) or renal dysfunction (creatinine clearance < 30 mL/min) Hypercalcemia (serum calcium greater than [>]0.25 millimoles per liter [mmol/L] [>1 milligram per deciliter {mg/d Hypo- (calcium [Ca] < 8.5 mg/dL) or hyper-calcemia (Ca > 10.5 mg/dL) Serum calcium > 11 mg/dL Calcium > 11 mg/dL