Used primarily as an internal standard in mass spectrometry and liquid chromatography-mass spectrometry (LC-MS/MS) analyses for the accurate quantification of estrone in biological samples such as serum, plasma, and urine. Its deuterated labels at positions 2,4,16,16 provide a distinct mass difference from the unlabeled compound, allowing clear differentiation during detection. This ensures high precision in measuring endogenous estrone levels, which is critical in endocrinology research, hormone metabolism studies, and clinical diagnostics related to estrogen-dependent conditions such as breast cancer, menopause, and reproductive disorders. The isotopic labeling minimizes interference from matrix effects and improves assay reproducibility.