Conducting studies on age-related morphometric parameters in the liver of rats not only provides valuable insights into basic biological processes but also aligns with the principles of sustainable development by promoting health research that can lead to more effective and environmentally conscious therapeutic interventions. These rodents are frequently used as laboratory models and possess a highly developed sexual instinct. About half of the testosterone entering the liver is converted to androsterone and regulates protein biosynthesis. Hepatocyte nucleus is the center of the cell and helps to detect various pathological abnormalities in the body. The aim of this study is to investigate the age-dependent morphometric responses of rat liver. Histologic study was performed according to the generally accepted rules. The area of lobes and nuclear-cytoplasmic ratio of hepatocytes were measured. Dynamic wave-like changes of classical lobules of rat liver in postnatal ontogenesis were presented. The reliable decrease of the index by 2-week age is connected with changes of physiological and morphological parameters. The increase of data in pubertal period is associated with the gain of body weight for the functioning of the musculoskeletal system. Moreover, insignificant wave-like changes at the stage of morphofunctional maturity of rats are associated with the age-related development of rodents. Changes in the number of hepatocytes depend on the physiological features of the hormonal background of male rats and the increase in body weight of animals.