What is Follicle-stimulating hormone (FSH)?

Follicle-stimulating hormone, or FSH, is a special message from your brain that helps control how your body makes eggs or sperm.

Imagine you have a mailbox in your head, this is where messages like FSH come from. When it's time to grow new eggs (in girls) or prepare for making sperm (in boys), the brain sends out an FSH message through the blood, like sending a letter to a friend who lives far away.

• In girls, FSH helps little pockets in the ovaries called follicles grow and get ready to release an egg.
• In boys, FSH helps the testicles make sperm, tiny swimmers that help you become a parent someday!

Think of FSH like a coach at a sports camp. It tells your body when it's time for a new round of play, whether that’s making eggs or sperm.

When FSH levels are high, it means your brain is saying, “Time to grow some new eggs or sperm!” And when they’re low, it’s like the brain is taking a break, just like you might after playing all day.