Several hormones can affect sexual desire and arousal, including estrogen, progesterone, and testosterone. However, the specific hormone that causes horniness is not clear-cut and may vary between individuals. Here are some key points about how these hormones affect sexual desire:

• Estrogen: Higher levels of estrogen in the body promote vaginal lubrication and increase sexual desire. Estrogen also plays a role in breast growth and development, pubic and underarm hair growth, and regulating stages of the menstrual cycle.

• Progesterone: Increases in progesterone can reduce sexual desire. Progesterone can also make individuals feel bloated, sluggish, and is associated with the undesirable symptoms of PMS.

• Testosterone: Testosterone plays a role in initiating sexual activities and pursuing sexual desire and behavior in both men and women. While testosterone is not directly linked to libido levels in females, it has a key role in repairing and maintaining reproductive tissues and bone mass.

Overall, hormones are just one factor that can influence sexual desire and arousal, and the specific hormone that causes horniness may vary between individuals.