Dihydrotestosterone (DHT) is a potent androgen hormone that stimulates the development of male characteristics. It is synthesized from testosterone by the enzyme 5-alpha reductase, primarily in peripheral tissues like the prostate, skin, and hair follicles. Although less than 10% of circulating testosterone is converted to DHT, it is many times more powerful than its precursor at the androgen receptor. DHT plays a significant role in development, contributing to the formation of male external genitalia in the fetus and promoting body and facial hair growth during puberty. In adulthood, its activity is linked to the health of hair follicles and the prostate gland.
Clinical Reasons for Measuring DHT
A physician may order a Dihydrotestosterone test when symptoms suggest an imbalance in androgen activity. A common reason is the investigation of androgenetic alopecia (pattern baldness), where increased DHT activity contributes to progressive hair thinning. The test can also be used to evaluate hirsutism in women, which is the excessive growth of dark, coarse hair in a male-like pattern.
DHT testing is relevant for diagnosing or monitoring specific developmental and metabolic conditions. Clinicians use it to assess for 5-alpha reductase deficiency, a condition where the enzyme is dysfunctional, leading to low DHT levels and ambiguous genitalia in genetically male infants. The test may also monitor the effectiveness of anti-androgen medications, such as 5-alpha reductase inhibitors, prescribed for conditions like benign prostatic hyperplasia (BPH) or hair loss. Assessing DHT levels, often alongside testosterone, provides a comprehensive view of androgen status.
Laboratory Methods for Checking DHT Levels
Measuring Dihydrotestosterone levels most commonly involves analyzing a blood sample, specifically the serum (the liquid portion of the blood after clotting). While fasting is not typically required, collecting the sample in the morning is preferred to standardize results against established reference ranges. This preference exists because steroid hormones, including DHT, exhibit a diurnal variation, meaning their concentration fluctuates throughout the day.
The laboratory technique used for analysis significantly impacts the reliability of the result. Older methods, such as immunoassays (IA), including radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA), are less specific and can overestimate the true DHT value due to interference from other steroids. The gold standard for measuring DHT in serum is now Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). This highly sensitive and specific technique accurately quantifies the low concentrations of DHT found in circulation, offering better precision, especially at lower levels seen in women or children.
While serum testing measures circulating DHT, other sample types offer different insights but are less standardized. Saliva testing measures the free, or bioavailable, fraction of DHT, which is the portion not bound to proteins and active in tissues. This method is sometimes used for monitoring topical treatments, but its reliability is generally lower than serum LC-MS/MS. Urine testing is the least common method for direct DHT assessment and typically measures hormone metabolites rather than the active hormone itself.
Interpreting DHT Test Results
The numerical result from a Dihydrotestosterone test is interpreted by comparing it to a reference range considered normal for a healthy population. These ranges are not universal and vary significantly based on the patient’s sex, age, the specific laboratory, and the testing method used. For instance, normal levels in adult males typically range from 30 to 85 nanograms per deciliter (ng/dL). Adult female ranges are much lower, often between 0 and 20 ng/dL.
An elevated DHT level in males is associated with androgenetic alopecia and can contribute to the development of benign prostatic hyperplasia (BPH). In women, high DHT may correlate with conditions like hirsutism and polycystic ovarian syndrome (PCOS). Conversely, a lower-than-normal DHT concentration can suggest a deficiency in the 5-alpha reductase enzyme or low overall testosterone levels (male hypogonadism).
A high or low number on a DHT test is not a diagnosis in itself. Results must always be considered in the context of a person’s physical symptoms, medical history, and other hormone test results, such as the testosterone-to-DHT ratio. A healthcare provider uses this comprehensive clinical picture to determine the underlying cause of any hormonal imbalance.