Final answer:
Hormones such as T3 and T4, which are secreted by the thyroid gland, and the physical exercise play a crucial role in increasing the metabolism rate, stimulating physical and mental growth, and influencing various body functions including the development of muscle mass and strength.
Step-by-step explanation:
The substance described in the question that increases metabolism rate, stimulates physical and mental growth, and induces targets to produce insulin-like growth factors (IGF) is likely a hormone such as T3 (triiodothyronine) or T4 (thyroxine), both of which are secreted by the thyroid gland. These hormones increase the metabolic rate in cells throughout the body. They play a critical role in body temperature regulation, normal growth, and brain development.
Additionally, physical exercise has been shown to increase blood flow and oxygen availability to the brain, stimulate the production of growth factors that promote new brain cells and new neuronal pathways, and increase serotonin levels, which can enhance memory retention and cognition, demonstrating another aspect of how metabolism and growth are interconnected with physical activity and endocrine function.
Moreover, other hormones produced by the testes in males and the ovaries in females contribute to muscle mass and strength increases, as well as bone growth and strengthening, indicating the multifaceted nature of hormonal impacts on metabolism and physical development.