DIHYDROTESTOSTERONE (DHT)

The Dihydrotestosterone (DHT) test measures the concentration of dihydrotestosterone in a blood sample. DHT is a potent androgen hormone produced when the enzyme 5-alpha-reductase converts testosterone into dihydrotestosterone in certain tissues.

DHT contributes to the development of male external genitalia before birth and supports androgen-dependent changes during puberty. In adults, it acts in tissues including the prostate, skin and hair follicles. Although DHT is derived from testosterone, the two hormones have different concentrations, tissue effects and clinical uses.

This test may support the assessment of androgen metabolism, suspected 5-alpha-reductase deficiency or the biochemical response to medicines that inhibit 5-alpha-reductase. It is generally interpreted with testosterone and other reproductive hormones rather than as an independent diagnostic test.

Benefits of the Test

• Measures circulating dihydrotestosterone concentration.
• Supports evaluation of suspected 5-alpha-reductase deficiency.
• Provides information about the conversion of testosterone into DHT.
• May help monitor treatment with 5-alpha-reductase inhibitors.
• Contributes to selected evaluations of abnormal androgen development.
• May be interpreted with testosterone during specialist endocrine assessment.
• Supports investigation of certain androgen-related clinical conditions.
• Provides a measurable baseline before or during selected treatments.

Why Doctors Recommend This Test

A doctor may recommend DHT testing when a disorder of testosterone metabolism is suspected. One established clinical use is evaluating possible 5-alpha-reductase deficiency, a rare condition in which the body cannot efficiently convert testosterone into DHT.

DHT is important for the development of male external genitalia. Reduced production due to 5-alpha-reductase deficiency may lead to atypical genital development or differences in sexual development. Diagnosis requires specialist evaluation and usually includes testosterone, DHT and other hormone tests, sometimes before and after hormonal stimulation.

The test may also be used to monitor patients taking medicines that inhibit 5-alpha-reductase, such as finasteride or dutasteride. These medicines reduce the conversion of testosterone into DHT and are prescribed for selected prostate or hair-loss conditions. A decreased DHT concentration may reflect the expected biochemical effect of treatment.

DHT is involved in androgen-dependent hair-follicle activity and may contribute to androgenetic alopecia in genetically susceptible individuals. However, a serum DHT result cannot independently diagnose male-pattern or female-pattern hair loss. Many affected people may have circulating DHT values within the laboratory reference interval because tissue sensitivity, androgen-receptor activity and genetic factors are also important.

DHT also acts within prostate tissue, but the blood DHT level cannot independently diagnose benign prostatic enlargement or prostate cancer. A normal result does not exclude prostate disease, and an elevated result does not confirm it. Prostate evaluation requires clinical assessment and other appropriate investigations.

In women, DHT may be considered during specialist investigation of androgen-related symptoms, such as excess facial or body hair, persistent acne or scalp hair thinning. More commonly used initial tests may include total testosterone, free testosterone, SHBG and DHEAS. The appropriate combination depends on the patient's symptoms.

Preparation Before Test

Fasting may not always be required, but follow the instructions provided by the doctor or laboratory. Because this is a specialised hormone test, the laboratory may specify a collection time or request that the sample be collected under standardised conditions.

Inform the doctor about finasteride, dutasteride, testosterone therapy, anabolic steroids, anti-androgen medicines, hormonal contraceptives, fertility treatments and all other prescribed or non-prescribed medicines. These may alter DHT production or affect result interpretation.

Do not stop finasteride, dutasteride, testosterone or any prescribed treatment without medical advice. If the test is being performed to monitor therapy, the doctor should determine when the sample should be collected in relation to the medicine.

Tell the healthcare professional about pregnancy, recent severe illness, hormonal treatment, chemotherapy or known endocrine conditions. Age, sex, developmental stage and treatment history are important for interpretation.

A healthcare professional collects blood from a vein, usually in the arm. Serum is commonly used for testing. The sample may require separation and specialised handling before being transported to the performing laboratory.

Normal Reporting Time

The Dihydrotestosterone test is a specialised investigation and is commonly reported within approximately 3–7 working days after the laboratory receives a suitable sample. The exact turnaround time may vary depending on the testing schedule, sample transport, analytical method, quality-control checks and result verification. Some referral-laboratory workflows may take longer.

Who Should Take This Test?

This test may be appropriate for patients undergoing specialist evaluation for possible 5-alpha-reductase deficiency or another disorder affecting testosterone-to-DHT conversion. It may also be requested to monitor the biochemical response to a 5-alpha-reductase inhibitor.

Doctors may consider DHT measurement during selected assessments of atypical sexual development, androgen imbalance or treatment response. It is not generally required as a routine fertility, hair-loss or prostate-screening test.

People with hair loss should not assume that a DHT test will identify the cause. Hair loss may be related to genetics, thyroid disease, nutritional deficiency, autoimmune disease, illness, stress, medicines or other factors. A clinician should select investigations based on the hair-loss pattern and medical history.

Detailed Information

DHT is generated from testosterone through the action of 5-alpha-reductase. Different forms of this enzyme are expressed in different tissues. Type 2 activity is prominent in genital tissues and the prostate, while type 1 activity is found in several tissues, including sebaceous glands.

DHT binds strongly to androgen receptors and produces androgenic effects in responsive tissues. It is also tightly bound to sex hormone-binding globulin in the bloodstream. Circulating DHT does not always reflect its concentration or biological effect inside a particular tissue.

A low DHT result may occur in patients taking a 5-alpha-reductase inhibitor or those with genetic 5-alpha-reductase deficiency. Interpretation may require calculating or assessing the relationship between testosterone and DHT, sometimes after specialist stimulation testing.

An increased result may reflect greater androgen production or conversion, medicine and supplement use or individual biological variation. A high value does not independently diagnose hair loss, prostate disease or another specific medical condition.

DHT testing may be performed using liquid chromatography with tandem mass spectrometry or another validated analytical method. Reference intervals can differ considerably according to sex, age, developmental stage, specimen type and laboratory method.

Children and adolescents require age- and puberty-stage-specific interpretation. Adult male and female reference intervals are also different. The reference range printed on the individual laboratory report should always be used.

The result may be considered with total testosterone, free testosterone, SHBG, LH, FSH, DHEAS, androstenedione and other investigations. Interpretation should be performed by an endocrinologist, andrologist, urologist or another qualified healthcare professional familiar with the patient's clinical history.