Androgen is a class of steroid hormones responsible for the development and maintenance of male characteristics, including secondary sex traits, reproductive function, and aspects of metabolism and behavior. Testosterone is the primary and most well-known androgen.
Androgens are synthesized primarily in the testes in males and the ovaries and adrenal glands in females. They act through intracellular receptors that bind DNA to regulate gene expression. These hormones influence physical development during puberty, sperm production, and libido throughout life.
The term "androgen" derives from Greek roots: *andros* (man) and *genēs* (producing), reflecting their role in masculine traits. While often associated with male biology, androgens are essential in both sexes, though in different quantities and functions.
Androgens exert their effects by binding to androgen receptors (AR) located in the cytoplasm of target cells. Once bound, the hormone-receptor complex translocates into the nucleus, where it regulates transcription of specific genes involved in growth, differentiation, and metabolic activity.
This process occurs in tissues such as the prostate, seminal vesicles, skin, hair follicles, skeletal muscle, and brain. For example, androgen receptor activation in muscle cells increases protein synthesis, contributing to greater lean body mass and strength. In the brain, androgens modulate mood, aggression, and sexual motivation.
Levels of circulating androgens are tightly regulated by the hypothalamic-pituitary-gonadal (HPG) axis. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary to secrete luteinizing hormone (LH). LH then signals the testes to produce testosterone. Negative feedback maintains homeostasis: high testosterone levels suppress further GnRH and LH release.
While testosterone dominates clinical discussion, several androgens exist, each with distinct roles and concentrations.
| Androgen | Primary Source | Relative Potency | Key Function |
|---|---|---|---|
| Testosterone | Testes (95%), Adrenals (5%) | 1.0 (reference) | Male sexual development, libido, muscle mass, red blood cell production |
| Dihydrotestosterone (DHT) | Peripheral conversion via 5α-reductase | 2-3× stronger than testosterone | Prostate growth, male pattern hair development, external genitalia formation |
| Androstenedione | Adrenal glands, gonads | ~0.1× testosterone | Weak androgen; precursor to testosterone and estrogen |
| Dehydroepiandrosterone (DHEA) | Adrenal cortex | Very low potency | Major adrenal androgen; precursor to sex steroids; declines with age |
Testosterone is the dominant androgen in men, with serum levels averaging 300-1,000 ng/dL. DHT, formed from testosterone by 5α-reductase enzymes in the skin, prostate, and liver, is more potent and acts locally in tissues with high enzyme activity. This explains why DHT drives male-pattern baldness and benign prostatic hyperplasia (BPH).
Non-male individuals also produce androgens. In women, the adrenal glands produce DHEA and androstenedione, while ovarian theca cells contribute small amounts of testosterone. Elevated androgen levels in women can lead to polycystic ovary syndrome (PCOS), marked by irregular cycles, acne, and hirsutism.
Androgens are not solely responsible for aggression or dominance. While animal studies show correlations between testosterone and aggressive behavior, human research shows context-dependent effects. A 2017 meta-analysis published in *Psychological Science* found that testosterone influences competitive behavior but not inherently violent tendencies.
Another misconception is that androgen replacement therapy (TRT) universally boosts energy, mood, and performance. The Endocrine Society guidelines (2022) state TRT is indicated only for men with symptomatic hypogonadism confirmed by low serum testosterone and elevated LH. Unnecessary use may increase risks of cardiovascular events and erythrocytosis.
A lesser-known fact: androgens play a protective role in bone health. Men with untreated hypogonadism have lower bone mineral density, increasing fracture risk. A 2020 study in *The Journal of Clinical Endocrinology & Metabolism* showed that TRT improved lumbar spine BMD by 3.2% over 12 months in hypogonadal men.
Consider a 45-year-old man presenting with fatigue, reduced libido, and decreased muscle mass. Blood work reveals a total testosterone level of 210 ng/dL (low), free testosterone at 3.1 pg/mL (low), and elevated LH at 12 mIU/mL (indicating primary testicular failure).
Diagnosis: Secondary hypogonadism due to idiopathic testicular insufficiency. Treatment: Intramuscular testosterone enanthate injections at 100 mg weekly. After six months, symptoms improved: energy returned, libido normalized, and muscle mass increased by 4.5 kg. Bone density scans showed a 2.1% improvement in lumbar spine BMD.
This case illustrates that androgen deficiency is diagnosable and treatable. However, treatment requires confirmation of low bioavailable testosterone and absence of contraindications like untreated sleep apnea or uncontrolled heart failure.
Low androgen levels in men correlate with metabolic syndrome, insulin resistance, and increased visceral fat. A 2019 cohort study in *The Lancet Diabetes & Endocrinology* found that men with testosterone below 300 ng/dL had a 60% higher risk of developing type 2 diabetes over five years, independent of BMI.
In women, excess androgen causes PCOS, affecting ~6-10% of reproductive-age women. Diagnosis involves clinical signs (hirsutism, acne, oligomenorrhea), elevated serum testosterone (>150 ng/dL), and ultrasound evidence of polycystic ovaries. Treatment includes combined oral contraceptives to suppress ovarian androgen production and metformin for insulin sensitivity.
High androgen levels in men can result from tumors (e.g., Leydig cell tumors), exogenous use (anabolic steroids), or rare genetic disorders like congenital adrenal hyperplasia. Exogenous androgen abuse leads to suppressed natural testosterone production, infertility, and gynecomastia.
Understanding what is androgen requires recognizing its biological diversity, regulatory complexity, and clinical significance. Androgens are not merely "male hormones"-they are important regulators of physiology across both sexes. Their proper function supports reproductive health, metabolic balance, and neuropsychological well-being.
For accurate diagnosis and management of androgen-related conditions, consult an endocrinologist. Hormonal imbalances require precise testing, not self-diagnosis based on symptoms or online quizzes.