What hormone is known for stimulating cell reproduction and healing?

Epidermal growth factor (EGF) is recognized for its role in stimulating cell reproduction, growth, and healing processes. It is a peptide that binds to its receptor on the surface of cells and initiates a cascade of biological responses that promote cellular proliferation and regeneration. This makes EGF particularly important in tissue repair and the healing of wounds, as it encourages the turnover of skin cells and helps maintain the integrity of the epidermis.

Other hormones and factors listed have different primary roles. For example, testosterone is primarily known for its effects on muscle and bone mass, as well as its influence on male secondary sexual characteristics, rather than specifically promoting cell reproduction and healing. Insulin mainly regulates glucose uptake and metabolism, affecting energy levels and fat storage, which does not centrally tie to the processes of cell reproduction and healing in the way EGF does. Estrogen plays a significant role in the female reproductive system and influences various functions related to reproduction, but its direct effect on wound healing and cell reproduction is less emphasized compared to that of EGF.

Thus, the property of EGF to directly stimulate the growth and healing of cells highlights its significance as the correct answer in this context.