The of this research were to identify the most important hormonal changes resulting of left nephrectomy of New Zealand rabbits (Oryctoagus cuniculus), such as: angiotensin-II (Ang-II), Erythropoietin (EPO), and Vitamin D₃ (Vit.D₃), and to clarify the relationship between the left nephrectomy and the heart through the atrial natriuretic peptide (ANP) hormone. Therefore, this study was conducted at the University of Mosul /College of Science /Department of Biology, for the period from April (2023) to August (2023). For this study, 60 white New Zealand rabbits used, and divided into four groups, each group consisting of 15 rabbits. As a result, the study showed that the concentration of the AngII hormone was significantly increased in rabbit group one month after nephrectomy compared to the rest of the groups. Followed by a noticeable decrease in the concentration of this hormone in rabbit group tow months after nephrectomy, and increased decrease in the concentration of this hormone in rabbit group three months after nephrectomy, but it didnt reached to the concentration of control group, at the probability level (P≤0.05). On the other hand, there was a significant decrease in the concentration of the EPO, ANP hormones and Vit.D₃ in rabbit group one month after nephrectomy. Then the concentrations began to rise after two months and reached its peak in rabbit group three months after nephrectomy, but it did not reach the level of control group, at the probability level (P≤0.05). Conclusions: It has been concluded in this study that the renal hormones contribute extensively to the physiologic functions of the kidneys and in many cases, other organs. The removal of one of the kidneys caused some physiological changes in some hormones.