Used as a stable isotope-labeled internal standard in mass spectrometry and gas chromatography for accurate quantification of androstenedione and related steroids in biological samples such as blood, urine, and saliva. Its isotopic enrichment allows clear differentiation from endogenous compounds, improving precision in hormone testing, doping control in sports, and clinical diagnostics of endocrine disorders. Also employed in metabolic studies to trace the biosynthesis and transformation pathways of androgens in human and animal models.