Prohormones are a class of substances that serve as precursors to hormones, meaning they are converted into active hormones within the body. These compounds have a minimal hormonal effect on their own due to their structure, which often prevents immediate binding to hormone receptors. Historically, prohormones gained popularity as supplements in the 1990s and early 2000s, before many became subject to regulation. The body naturally produces prohormones, such as proinsulin, to regulate hormone expression.
Understanding Prohormones
Prohormones are typically steroidal molecules that differ structurally from active hormones like testosterone. They are designed to undergo metabolic activation once ingested, often through enzymatic processes primarily occurring in the liver. For instance, androstenedione can be converted into testosterone through the action of the enzyme 17β-hydroxysteroid dehydrogenase. This conversion process transforms the inactive prohormone into an active anabolic hormone, such as testosterone or nandrolone (19-nortestosterone), which can then bind to androgen receptors in cells.
Unlike anabolic steroids, which are synthetic forms of active hormones and are already in their active state upon ingestion, prohormones require this internal conversion to exert their effects. This distinction is significant because prohormones are not hormones themselves but rather compounds that initiate a biological pathway to increase hormone levels in the body. While natural prohormones like dehydroepiandrosterone (DHEA) and androstenedione exist, many prohormones found in supplements are synthetic precursors intended to boost specific hormone levels.
Intended Effects and Appeal
Individuals use prohormones to enhance physical performance and alter body composition. The appeal stems from their ability to increase levels of anabolic hormones like testosterone, which are associated with muscle growth. Users seek accelerated muscle growth during bulking phases and increased strength and power output during training.
Prohormones are also used for improved recovery after intense workouts. Some users also aim for body recomposition, reducing fat mass while increasing or preserving lean muscle tissue. These perceived benefits drive their use among athletes and bodybuilders to enhance their physique and athletic capabilities.
Health Risks and Adverse Effects
The use of prohormones carries several health consequences, with liver toxicity being a significant concern. Many prohormones, especially those that are 17-alpha methylated, place considerable stress on the liver, leading to a high risk of hepatotoxicity. This can manifest as jaundice or elevated liver enzymes.
Prohormone use can also lead to cardiovascular issues. These substances may negatively impact cholesterol ratios, specifically raising low-density lipoprotein (LDL) and lowering high-density lipoprotein (HDL) levels, and can contribute to increased blood pressure. Such changes can elevate the risk of heart disease.
Hormonal imbalances are another common adverse effect, as prohormones can suppress the body’s natural testosterone production. This suppression can result in conditions such as gynecomastia (enlargement of male breast tissue), testicular atrophy, acne, and hair loss. The hypothalamic-pituitary-testicular (HPT) axis, which regulates natural hormone production, can take months or even years to recover after discontinuing prohormone use, and in some cases, recovery may be incomplete.
Psychological effects are also associated with prohormone use, including aggression and mood swings. Users may experience lethargy, brain fog, or appetite loss, which are often linked to low estrogen levels, liver overload, and hormonal suppression. These effects highlight the impact prohormones can have on both physical and mental well-being.
Regulatory Status and Availability
The legal classification of prohormones has evolved in the United States. The Anabolic Steroid Control Act of 2004 expanded the definition of anabolic steroids to include a broader range of testosterone-related substances, classifying many prohormones as Schedule III controlled substances. This legislation removed them from the dietary supplement market.
This legal framework impacts the sale, possession, and use of these compounds, making their distribution for non-medical purposes a criminal offense. Despite these regulations, some substances related to banned prohormones may still be found, often marketed under different names. Their availability can vary, with some being sold through unregulated online channels or as “research chemicals.”