Which factor is NOT a cause of intrinsic aging?

Intrinsic aging refers to the natural aging process that occurs over time due to internal factors, primarily influenced by genetics and biological processes rather than external factors. Genetics plays a crucial role as it determines the baseline characteristics of an individual's skin and overall physiology. Hormonal changes also contribute to intrinsic aging, affecting skin elasticity, moisture retention, and overall health. Metabolism influences how the body processes nutrients and maintains cellular function, impacting the aging process on a cellular level.

Sun exposure, however, is an external factor that significantly accelerates aging—often referred to as extrinsic aging. It can lead to skin damage, wrinkles, and other signs of aging that would not occur solely due to the body's natural aging process. Therefore, sun exposure does not fall under the category of intrinsic aging causes and is the correct answer.