What substance is produced that influence both the reproductive cycle and the development of sex characteristics in?

The substance produced that influences both the reproductive cycle and the development of sex characteristics is primarily sex hormones, such as estrogen and testosterone. Estrogen plays a crucial role in the female reproductive cycle, regulating menstruation and supporting the development of secondary sexual characteristics. Testosterone is key for male reproductive health, influencing sperm production and the development of male secondary sexual characteristics. Both hormones are essential for the proper functioning of the reproductive system in both sexes.