Used as a stable isotope-labeled internal standard in mass spectrometry-based assays for the quantitative analysis of estrone sulfate in biological samples such as serum, plasma, and urine. Its deuterated structure allows for accurate differentiation from endogenous estrone sulfate, improving measurement precision in hormone metabolism studies, clinical diagnostics, and pharmacokinetic research. Also employed in metabolic studies to trace estrogen pathways and assess hormonal imbalances.