Estrogen stimulates breast cells and signals the uterus to develop a protective lining in preparation for a possible fertilized egg each month. But it affects much more than reproduction—it also plays a vital role in bone and skin health, promotes clear thinking and concentration, and boosts confidence.

Released at ovulation, progesterone maintains the uterine lining, supports pregnancy, and keeps estrogen in check. It is also a calming agent that reduces anxiety and promotes sleep.

Testosterone encourages libido and boosts ambition in women as well as men. "Testosterone gives us our drive to get things done and to reproduce and to be in the extroverted world we're in," explains Steelsmith. It's also a potent bone-builder, it helps us form and maintain muscle, and it regulates levels of body fat.

Manufactured by the pancreas, insulin transports sugar from your blood to your cells and is a key player in regulating body weight.

Thyroid hormone
Facilitates and controls metabolism rate in every cell of the body, and regulates energy levels, body weight, and body temperature. Thyroid hormone also has a direct effect on the levels of adrenal and sex hormones—making it even more important to keep in balance.

What the body releases in times of immediate stress—such as a car accident or a confrontation—to give you the stamina to flee or the strength to fight. This powerful chemical boosts blood glucose levels, raises blood pressure, and facilitates delivery of blood to the muscles.

Cortisol is the body's answer to ongoing stress—such as a high-traffic commute or job pressure. It works much more slowly than adrenaline, although it also raises blood glucose levels. When balanced, levels of cortisol are high in the morning—allowing you to face the challenges of your day—but low in the evening, so you can rest well.

The body's most abundant hormone. Balances cortisol and aids in the formation of estrogen and testosterone. Promotes muscle strength, boosts immunity, increases sex drive, and enhances mood. Encourages new bone growth and prevents the depletion of calcium from your bones. Sadly, your body starts producing less of this wonder chemical as early as your 20s.