Throughout the life cycle of organisms, nutrient intake is necessary for the maintenance of the functions of daily life and in preparation for a variety of biological events, such as molting, migration, hibernation, and reproduction. One of the most energetically costly events is reproduction. Present study sought to elucidate the seasonal variations in the markers of intermediate metabolism (total proteins, uric acid, glucose, total lipids, triglycerides, total cholesterol, VLDL cholesterol, and glycogen) and body condition indices (gonadossomatic, hepatosomatic, and abdominal fat index) in Tropidurus catalanensis, in order to know the physiological costs of reproduction in this species, also allowing these parameters to be used as markers in studies of environmental alterations. During the study period, 38 males and 35 females were collected. Tropidurus catalanensis is a lizard that inhabits the Pampa grasslands, a biome that stretches across Argentina, Brazil, and Uruguay. Results obtained reveal that this lizard exhibits a clear pattern of seasonal variation in its metabolism, as reflected mainly in levels of plasma total protein, liver glycogen, total lipids, and triglycerides in males and females; and in blood glucose and lipid, and liver protein levels in females. It bears stressing that all body condition indices analyzed varied over the course of the year. The parameters studied can be used to evaluate the impact of changes in environmental conditions on these animals. Winter months appear to trigger a reduction in overall metabolism, most intensely in males. Reproductive period seems to be the biological event that demands greater energy demand, leading to the mobilization of energy stocks mainly in females, where the search for food may be reduced in the months of reproductive peak (spring). The response pattern observed during the reproductive period suggests that this time represents a critical point in terms of the animal's adaptation to its life cycle.