Testosterone is the hormone most responsible for sexual development and body composition in men. Testosterone production increases with the onset of puberty and usually peaks in most males during their late teens or early twenties.

Choosing a safe testosterone boost can be difficult because safety is often a relative term, depending on the user. For example, individuals younger than 30 years of age still have optimal testosterone levels. Boosting testosterone may benefit younger users when it comes to muscle building and fat burning.

Steroids are a type of hormone produced by the body to contribute to cell function, muscle and tissue building, and stress and growth regulation. Corticosteroids are a type of manufactured prescription drug product given to mimic or enhance the effects of the body's natural steroids.

Testosterone fills many important functions, from maintaining bone density and muscle mass to regulating sex drive and sperm production. High testosterone alone does not necessarily cause problems or need to be treated; it all depends on how high the levels go and your overall health.

Testosterone is a steroid hormone secreted from the adrenal glands, ovaries and testes. The hormone plays a crucial role in maintaining a healthy libido, preserving bone structure and muscle mass and maintaining energy levels. The thyroid gland plays an important role in maintaining natural testosterone levels.

Polycystic ovary syndrome, or PCOS, is the most common metabolic hormonal disorder affecting women of reproductive age. The exact cause is unknown, but there appears to be a genetic component.

There are scores of health issues related to cow's milk -- the growth hormones and pesticides used to produce milk. In fact, according to Dr. Joseph Mercola, cow's milk is the number one allergic food in the United States.

Steroids are a class of lipid hormones synthesized from cholesterol. They regulate metabolism, immune response, reproduction and other essential biological processes, the 1999 textbook “Biochemistry” notes.

Progesterone is a female hormone that your doctor may prescribe to help you if you have passed through menopause, MedlinePlus states. Along with another female hormone called estrogen, progesterone can help as a hormone replacement therapy. It works to decrease the potential of cancer developing in your uterus.

Testosterone supplements are products that increase the male sex hormone testosterone, which governs muscle mass, aggression and secondary sexual characteristics in men. Prohormones, testosterone boosters and estrogen blockers are all different types of testosterone supplements.

If you have polycystic ovarian syndrome, or PCOS, your ovaries produce an excess of androgens--the group of male hormones that includes testosterone. Such an excess can lead to a number of troublesome symptoms, such as acne, excess body hair and fertility problems.

Growth hormone is a protein produced by the pituitary gland, which is a pea-sized gland located below the brain. Growth hormone is one of the hormones critical for normal growth in children and adolescents, and it is also involved in regulating metabolism. In adults, growth hormone deficiency is extremely rare.