Seventy-two gonadectomized male and female albino rats were used in the present study. They were divided into six groups, group A served as control, group B injected with Es+Prog. (mammogenesis), group C treated with Es+ Prog. +PRL (lactogenesis). The last three groups are lactogenic and treated with alloxan (D); insulin (E) and alloxan and insulin (F). Serum TSH, T3, T₄, Ca, P, glucose, total protein and total lipids were estimated. Mammary tissues were isolated for determination of Ca, P, total protein and total lipids. Lactogenesis in the present study elevated release of thyroid hormones and the data proved the active role of insulin during this process. Induction of diabetes during lactogenesis increased TSH without any change in serum T3 and T4. Lactogenesis and insulin injection after alloxan increased serum and tissue total lipids and tissue total protein. Phosphorus measurement showed a significant increase after injection of insulin in lactogenic males and in lactogenic males and lactogenic females treated with alloxan and insulin. Calcium content of mammary tissues was increased in female lactogenic animals and lactogenic males and females treated with insulin. It is concluded from above data that diabetes in lactogenic animals have an adverse effect on hormonal and biochemical levels in the mammary tissues and sera and injection of insulin may Change this effect.