This paper explores the phenomenon of gendered identity transformation in aging cisgender men, with a focus on the physiological, hormonal, psychological, and symbolic effects of testosterone decline across the lifespan. While gender identity is often treated as stable in adults, we argue that male-phase identity undergoes gradual but significant drift during andropause and late life. The loss of testosterone contributes not only to changes in libido, body composition, and cognitive functioning, but also to the emergence of feminized traits and a collapse of the sexually differentiated state. This transition is rarely acknowledged in clinical frameworks or social discourse. We frame this change as a natural identity-phase regression, which can be interpreted as a partial return to an earlier, more sexually neutral or mixed phenotype. Drawing from endocrinology, gerontology, cognitive psychology, and life-span studies, we propose that cisgender male aging represents a form of involuntary gender transition that has been insufficiently mapped. We further suggest that transgender individuals offer an early model of how to intentionally navigate such identity changes, and that insights from trans endocrinology and gender stabilization may be applicable in developing future aging protocols. This paper remains compliant with framing and focuses on longevity and aging research within a standard medical and scientific lexicon. Men transation with age!! “In this paper, the term ‘gender identity change’ is used in a broader sense to indicate shifts in gendered embodiment, role orientation, and phenotypic expression with age, rather than implying a wholesale change in self-identified gender.”