PTH and secondary hyperparathyroidism: In the present study, Wistar rats were fed on a customized vitamin-D-deficient diet to induce hypovitaminosis D. All vitamin-D-deficient groups (GP-1, GP-2, GP-3, GP-4, GP-5 and GP-6) showed variable degrees of secondary hyperparathyroidism (PTH > 65 pg/mL cutoff value, [40]), normal calcium (range 5.3–13 mg/dL [41]), low serum phosphorus levels (range 2.7–4.5 mg/dL [42]) and increased alkaline phosphatase levels (range 44 to 147 IU/L [43]).