Androgen receptors are proteins that detect testosterone and related hormones, then translate those chemical signals into changes in your cells. They belong to a family of nuclear receptors, meaning they work inside the cell nucleus to switch genes on or off. Every time testosterone influences muscle growth, bone density, hair patterns, mood, or reproductive development, it does so by binding to one of these receptors. Without functioning androgen receptors, your body would produce androgens but be unable to respond to them.
How Androgen Receptors Work
The androgen receptor sits quietly in the cytoplasm of a cell, held in an inactive state by chaperone proteins called heat shock proteins. When testosterone or its more potent form, dihydrotestosterone (DHT), enters the cell and docks onto the receptor, the receptor changes shape. That shape change causes it to release the chaperone proteins, pair up with a second receptor, and travel into the nucleus of the cell.
Once inside the nucleus, the receptor pair latches onto specific stretches of DNA and acts as a transcription factor, essentially a switch that tells the cell to read certain genes and produce the proteins they code for. One well-known target is the gene responsible for prostate-specific antigen (PSA). But there are hundreds of androgen-responsive genes across different tissues, which is why testosterone has such wide-ranging effects throughout the body.
When androgen levels drop and the hormone detaches, a built-in export signal shuttles the receptor back out of the nucleus and into the cytoplasm, resetting the cycle.
DHT vs. Testosterone at the Receptor
Both testosterone and DHT activate the same receptor, but they don’t bind with equal strength. DHT grips the receptor more tightly and holds on longer. In studies measuring how quickly each hormone dissociates from the receptor, DHT stayed bound with a half-life of about 40 hours, compared to roughly 15 hours for testosterone. This is why tissues that convert testosterone into DHT, such as the prostate, skin, and hair follicles, experience a stronger androgenic signal. An enzyme called 5-alpha reductase handles that conversion, and drugs that block it are commonly used to treat hair loss and enlarged prostate.
Where Androgen Receptors Are Found
Androgen receptors aren’t limited to reproductive organs. They’re expressed in muscle, bone, skin, liver, the cardiovascular system, fat tissue, and the brain. This broad distribution explains why changes in testosterone levels can affect so many aspects of health at once, from body composition and energy to skin oiliness and mood.
In the brain, androgen receptors are concentrated in the hippocampus (involved in memory) and the prefrontal cortex (involved in planning and decision-making). Studies of men undergoing androgen deprivation therapy for prostate cancer show measurable declines in short-term memory, mental flexibility, and executive function. Research on older men with low testosterone has found that supplementation can improve verbal memory, global cognition, and depressive symptoms, pointing to a meaningful role for these receptors in mental health.
What Androgen Receptors Do in Specific Tissues
In muscle, androgen receptor activation promotes protein synthesis, which is the fundamental reason testosterone builds muscle mass. In bone, receptor signaling supports mineral density and bone turnover. In bone marrow, androgen receptors are present on red blood cell precursors, and their activation stimulates red blood cell production. This is why men typically have higher red blood cell counts than women, and why testosterone therapy can raise hemoglobin levels.
In skin and hair follicles, androgen receptor activity drives both acne and pattern baldness in genetically susceptible people. The receptor responds to local DHT concentrations, which is why hair loss treatments often target the enzyme that produces DHT rather than the receptor itself.
Androgen Insensitivity Syndrome
The clearest demonstration of how critical these receptors are comes from androgen insensitivity syndrome (AIS), a genetic condition in which the receptor doesn’t function properly. People with AIS have XY chromosomes and produce normal or elevated levels of testosterone, but their bodies can’t respond to it.
More than 550 different genetic variants in the androgen receptor gene have been identified as causes. Some variants impair the receptor’s ability to bind hormones. Others prevent it from attaching to DNA. The result depends on severity. In complete androgen insensitivity, a person develops typically female external anatomy despite having XY chromosomes and internal testes. In partial forms, the degree of masculinization varies widely. The condition illustrates that producing androgens is only half the equation: without working receptors, those hormones have no effect.
The Role in Prostate Cancer
Prostate cells depend on androgen receptor signaling to grow, which makes the receptor both essential for normal prostate function and a vulnerability in cancer. The standard treatment for advanced prostate cancer is to cut off the supply of testosterone, starving cancer cells of the signal they need.
The problem is that prostate cancers often find workarounds. In about 30% of recurrent cases after androgen deprivation, the cancer cells amplify the androgen receptor gene, producing extra copies of the receptor so they can detect and respond to the tiny amounts of androgen still circulating. Other cancers develop mutations that broaden what the receptor recognizes, allowing it to be activated by adrenal hormones or even by drugs designed to block it. Still others overexpress the receptor, becoming hypersensitive to low hormone concentrations. This is the basic mechanism behind castration-resistant prostate cancer, one of the most challenging forms of the disease to treat.
Newer drug strategies aim to destroy the receptor protein entirely rather than just blocking it. One approach uses specially engineered molecules that tag the androgen receptor for disposal by the cell’s own recycling machinery, potentially overcoming the resistance mechanisms that defeat conventional hormone therapies.
SARMs and Tissue-Selective Activation
Selective androgen receptor modulators, commonly known as SARMs, are compounds designed to activate the androgen receptor in some tissues (like muscle and bone) while minimizing activity in others (like the prostate and skin). Traditional anabolic steroids activate the receptor everywhere, which is why they carry side effects ranging from acne and hair loss to prostate enlargement.
SARMs achieve selectivity in a few ways. Because they aren’t structurally similar to testosterone, they can’t be converted into DHT by 5-alpha reductase, removing one amplification pathway in androgenic tissues. They also can’t be converted into estrogen, which eliminates another category of side effects. Most importantly, when a SARM binds the receptor, it bends the receptor into a slightly different shape than testosterone or DHT would. That different shape attracts a different set of helper proteins (called coregulators), which in turn switches on a different set of genes depending on the tissue. Research comparing the signaling pathways activated by a SARM versus DHT found significant differences in which genes were turned on and which coregulators were recruited.
SARMs are not approved for general use and remain under investigation, but the concept behind them reveals something important about how the androgen receptor works: it isn’t simply an on/off switch. The shape it takes when bound to a ligand determines what it does, and different ligands produce meaningfully different outcomes across tissues.
The Receptor’s Structure
The androgen receptor protein has three main sections. The ligand binding domain at one end is where testosterone or DHT physically attaches. The DNA binding domain in the middle contains two zinc finger structures that recognize and grip specific sequences of DNA. Connecting them is a hinge region that contains the signal directing the receptor into the nucleus.
At the other end, the N-terminal domain is the most variable part of the receptor and is responsible for driving gene transcription at full strength. This domain is also where most of the differences between individuals show up, including variations in a repeating DNA sequence (a polyglutamine tract) that has been linked to differences in receptor sensitivity. The DNA binding domain, by contrast, is nearly identical across all steroid hormone receptors, reflecting its ancient and essential role in reading DNA.