The tensile strength of bone derived from collagen fibres, extend primarily along the lines of tensile force. For normal development and function of human skeleton, thyroid hormones are vital, which evidently visible in hyperand hypothyroid conditions. Earlier studies suggest that, Thyroid effect on collagen is dose dependent, tissue specific and sometimes controversial. Hypothyroidism causes impaired bone formation and growth retardation whereas hyperthyroidism may retard collagen synthesis and decelerate the bone mass. Hydroxyproline and hydroxyllysine are essential for the collagen cross linking and strength of the bone. Hydroxyproline estimation is considered as an index of collagen metabolism. The aim of the present study is to find out the changes in collagen characteristics in bone tissue of thyroxine treated common Indian toad. As common toad (Duttaphyrnus melanostictus) is studied extensively to have an elementary knowledge on the anatomy of vertebrates, the above species is used as the experimental organism in the present study. The method of Neuman and Logan (1950) modified by Leach (1960) was used to find out the hydroxyproline content from which the collagen contents were found out at two different doses of thyroxine (2.0 μg/gm & 0.5 μg/gm).

Keywords: Bone; Collagen, Thyroxine, Hydroxyproline.