The two most important macrominerals calcium and phosphorus are required for bone growth and body function of animals. The present study is designed to investigate the role of thyroid hormone i.e. triiodothyronine (T3) in regulating the levels of calcium and phosphorus in blood, muscle and bone of Indian toad, Bufo melanostictus. The response of poikilotherms to the thyroid hormones is dose dependent. The calcium and phosphorus content of three extracts of blood, muscle, bone tissues were estimated independently by the method of Kramer and Tisdall (1921) as modified by Clark and Collip (1925) and the method of Fiske and Subbarow (1925) respectively. There is an enhancement of calcium and phosphorus concentrations in blood, muscle and bone tissue at both the dose levels except for bone at higher dose T3 treatment for 7 days. Treated animals show an increased level of calcium and decreased level of phosphorus of bone. Tissue specific action showing the increase in calcium and phosphorus levels at higher dose is much more as compared to that of lower dose level in blood and muscle tissue. In contrast to young and immature animals, the adults and old animals may show certain differential response because of the interplay of other hormones such as gonadal and corticosteroids & growth hormone which appears in adult stage.

Keywords: Triiodothyronine(T3); Calcium; Phosphorus; Bufo Melanostictus.