You probably know that testosterone is a male sex hormone and cholesterol is a substance that travels in your blood, but you may be unaware that the two compounds are chemically related and that testosterone might influence the amount and type of cholesterol your body produces. Understanding how the two compounds relate to each other is an area of current research with potential implications for maintaining good health.

Two Essential Compounds​
Testosterone and cholesterol are both called steroids because they share a similar chemical structure, and both are also important for many bodily functions. Cholesterol is part of every cell's outer membrane, responsible for its fluid nature and helping determine which molecules can enter the cell. It's also a precursor for the synthesis of many compounds, including testosterone. Your body can obtain cholesterol from animal-based foods, but it's also made as needed by your liver and other organs. Testosterone is a sex hormone made in large amounts in the testes of men and in smaller amounts in women's ovaries. It stimulates sperm production and sexual function in men and may support a normal libido in women.

Transport in Blood
As steroids, testosterone and cholesterol are insoluble in water-based fluids such as blood. Because of this, your body has special mechanisms that allow the compounds to travel through your circulatory system to reach your organs and tissues. Testosterone binds to a special blood protein, called sex hormone binding globulin, forming a soluble complex that can be transported through your blood vessels, reaching cells called target cells because they respond to the hormone. A special but slightly different system allows cholesterol to travel in blood. Your liver cells combine cholesterol with protein to make compounds called lipoproteins, which transport cholesterol through your blood vessels to reach your cells and tissues.

Their Relationship
Low density lipoprotein, or LDL, is called "bad" cholesterol because high levels can cause potentially dangerous fatty deposits to form in your arteries. High density lipoprotein, or HDL, is called "good" cholesterol because it carries excess blood cholesterol back to the liver for removal. Research suggests that extra testosterone might affect blood levels of total cholesterol and HDL. For example, a study published in the March 2012 issue of "Substance Abuse Treatment, Prevention and Policy" reported that a single dose of extra testosterone in male subjects caused an increase in both total cholesterol and the liver enzyme that makes cholesterol. A review published in the September 2005 issue of "Clinical Endocrinology (Oxford)" concluded that testosterone might reduce HDL in some middle-aged men, although the authors reported that this possibility needs further study.

Changing Levels
Experts at Harvard Medical School summarize the changes in testosterone levels that can accompany age and the complex relationship between these changes and the risk of high cholesterol and cardiovascular disease. They indicate that testosterone tends to fall slowly as men age but caution that more research is needed to determine if testosterone therapy is advisable in older men, stating that high doses of the hormone might raise LDL levels and lower HDL levels. If you have questions about the relationship between cholesterol and testosterone, discuss them with your doctor.