Androsterone is a naturally occurring steroid molecule categorized as a weak androgen, a type of male sex hormone. It is a key metabolite, or breakdown product, of the more potent hormones testosterone and dehydroepiandrosterone (DHEA). Its biological activity is significantly less powerful than that of testosterone. This compound is found in both males and females and plays a part in the complex system of human hormone regulation.
How Androsterone Is Produced
Androsterone is formed as an end-product of metabolism, mainly in the liver, from its precursors, testosterone and DHEA. These initial androgens are produced in the adrenal glands, the testes in males, and the ovaries in females. The metabolic route involves several enzymatic steps that convert the active hormones into less-active forms.
One major pathway begins with testosterone being converted into dihydrotestosterone (DHT) by the enzyme 5α-reductase, which then transforms this into androsterone. DHEA, secreted in large amounts by the adrenal glands, also serves as a direct precursor processed by similar enzymes. This process effectively deactivates the more potent precursor hormones. Once formed, androsterone is prepared for excretion, primarily through the urine.
Biological Effects
Androsterone can bind to androgen receptors to influence male characteristics, though its effect is approximately one-seventh the potency of testosterone. Consequently, its influence on features like muscle mass or the development of male secondary sexual characteristics is minor compared to its parent hormones. Its presence mainly reflects the total metabolic turnover of stronger androgens.
Beyond its hormonal role, androsterone acts as a neurosteroid within the nervous system. It functions as a positive allosteric modulator of the GABAA receptor, the main inhibitory receptor in the brain. This interaction can have an inhibitory effect on brain activity and possesses anticonvulsant properties.
The compound is also known for its role in human chemosignaling, as it is excreted in sweat and urine. Androsterone has a musky odor for those who can perceive it and is considered a putative human pheromone. Studies have investigated its potential to affect mood and social perception, though the evidence for a true pheromonal effect in humans remains speculative.
Measuring Androsterone Levels
Androsterone is a component of metabolites historically measured together as 17-ketosteroids (17-KS). The total amount of 17-KS in a 24-hour urine collection was traditionally used to assess the function of the adrenal cortex. Elevated or decreased levels of 17-KS can suggest underlying conditions like Cushing’s syndrome, Addison’s disease, or congenital adrenal hyperplasia (CAH). Since most of these metabolites originate from the adrenal glands, 17-KS testing acts as a general indicator of adrenal health.
Modern medical practice favors specific serum (blood) tests for active hormones like testosterone, rather than the older 17-KS urine test. This is because 17-KS measurements, which include androsterone, do not reliably distinguish between different causes of hormone imbalance. Blood testing for androsterone is available, but it is often performed for research rather than as a primary diagnostic tool for routine clinical care. Measuring androsterone is most useful when evaluating the overall metabolic breakdown and inactivation processes of androgens.