Age-related decline is caused by cumulative damage to large molecules, cells, tissues, and organs. Rejuvenation interventions seek to prevent or remedy this damage. It is crucial to distinguish rejuvenation from mere life extension; the former involves slowing or reversing aging, necessitating the repair of age-related damage and the renewal of tissues. While rejuvenation can extend life, increasing longevity alone does not imply rejuvenation. This approach echoes the Ayurvedic concept of Rasayana, which intrinsically links rejuvenation and regeneration.
Science recognizes that levels of several essential hormones, such as growth hormone, testosterone, thyroid hormones and sex hormones (estrogen and progesterone), as well as erythropoietin, insulin, DHEA and melatonin, progressively decrease with age. In view of this, scientists have suggested that replacing these hormones could be advantageous in protecting against the damage caused by aging, as well as in correcting and restoring them in various tissues, organs and functions of the body. Initial experiments in laboratory animal models have already indicated promising results with regard to partial rejuvenation.