RESUMEN
This study focuses on the comparative metabolic profiling and effects of two steroid types: natural and synthetic, specifically 17α-methyl testosterone (17α-MT) at varying concentrations (1.5, 2, and 3 mg/kg) in rainbow trout (Oncorhynchus mykiss). Over a 75-day feeding trial, growth metrics, such as feed efficiency, daily specific growth, live weight gain, total weight gain, and survival rate were systematically monitored every 15 days. At the end of the feeding trial, histopathology, immunohistochemistry, and metabolome analyses were performed in the high-concentration groups (3 mg/kg natural and 3 mg/kg synthetic), in which the lowest survival rate was determined. Key findings reveal that the type of hormone significantly influences growth parameters. While some natural steroids enhanced certain growth aspects, synthetic variants often yielded better results. The metabolomic analysis highlighted significant shifts in the metabolism of tryptophan, purine, folate, primary bile acids, phosphonates, phosphinates, and xenobiotics via cytochrome P450 pathways. Histopathologically, the natural hormone groups showed similar testicular, hepatic, muscular, gill, cerebral, renal, and intestinal tissue structures to the control, with minor DNA damage and apoptosis observed through immunohistochemistry. Conversely, the synthetic hormone groups exhibited moderate DNA damage and mild degenerative and necrotic changes in histopathology.