Dihydrotestosterone (DHT) - Free

The Dihydrotestosterone (DHT) – Free test measures the unbound fraction of dihydrotestosterone circulating in the blood. DHT is a potent androgen formed when the enzyme 5-alpha-reductase converts testosterone into dihydrotestosterone within androgen-responsive tissues.

Most circulating DHT is attached to proteins, particularly Sex Hormone-Binding Globulin (SHBG), with a smaller amount bound to albumin. Only a very small fraction remains unbound or free. This free fraction is considered available to enter tissues and interact with androgen receptors.

The Free DHT test is a specialised investigation and is different from a standard total serum DHT test. Depending on the laboratory method, the report may include total DHT, the percentage of free DHT and the calculated or directly assessed free DHT concentration. Results require specialist interpretation alongside symptoms and other hormone measurements.

Benefits of the Test

• Measures the unbound fraction of circulating dihydrotestosterone.
• Provides information about DHT available to interact with body tissues.
• Supports specialised evaluation of androgen utilisation and metabolism.
• May contribute to the assessment of suspected 5-alpha-reductase deficiency.
• Can be interpreted when changes in binding proteins may affect total hormone values.
• May support monitoring of selected treatments affecting DHT production.
• Provides additional information when total DHT does not explain clinical findings.
• Uses specialised analytical techniques for low-concentration hormone measurement.

Why Doctors Recommend This Test

A doctor may recommend Free DHT testing when a detailed assessment of androgen availability is required. This may occur when symptoms and total androgen results do not agree or when changes in hormone-binding proteins may affect the interpretation of total DHT.

DHT is produced by the reduction of testosterone through 5-alpha-reductase. One established clinical application of DHT measurement is the evaluation of suspected 5-alpha-reductase deficiency. This rare condition can reduce DHT production and affect male external genital development. Diagnosis requires specialist hormonal and clinical assessment and cannot be established by Free DHT alone.

The test may also be used during specialised monitoring of medicines that inhibit 5-alpha-reductase, including finasteride and dutasteride. These medicines reduce testosterone-to-DHT conversion. The treating doctor should decide whether Free DHT testing is necessary and how the result should influence management.

DHT acts in tissues such as the prostate, skin and hair follicles. It may contribute to androgenetic alopecia in genetically susceptible people. However, neither total nor free DHT can independently diagnose the cause of hair loss. Tissue sensitivity, androgen-receptor activity, genetics, thyroid status, nutrition, illness and other factors may also be involved.

A Free DHT result cannot diagnose benign prostatic enlargement or prostate cancer. Circulating concentrations may not represent DHT activity within prostate tissue. Prostate symptoms require clinical examination and other investigations selected by the doctor.

In selected women, Free DHT may be considered during specialist assessment of androgen-related symptoms such as excess facial or body hair, acne, scalp hair thinning or menstrual irregularities. Initial investigations more commonly include testosterone, SHBG and DHEAS, with further tests based on clinical findings.

Preparation Before Test

Follow the exact preparation instructions provided by the doctor or laboratory. Fasting may not always be essential, but a fasting morning sample may be requested to standardise the assessment with other androgen tests.

Inform the doctor about finasteride, dutasteride, testosterone therapy, anabolic steroids, anti-androgens, hormonal contraceptives, fertility medicines, corticosteroids and all supplements. These may alter DHT production, binding or interpretation.

Do not stop any prescribed medicine without medical advice. When the test is intended to monitor treatment, the doctor should determine the collection time in relation to the medicine and previous doses.

Tell the healthcare professional about pregnancy, recent severe illness, hormonal treatment, chemotherapy, known endocrine disorders and recent major weight changes. These factors may affect hormone concentrations or binding proteins.

A healthcare professional collects blood from a vein, usually in the arm. Serum or plasma may be required depending on the validated method. The separated sample may need to be frozen and transported under controlled conditions to a specialised reference laboratory.

Normal Reporting Time

The Free Dihydrotestosterone test uses specialised methods and is commonly reported within approximately 9–15 days after sample pickup or receipt by the performing laboratory. Additional time may be needed for sample transport, testing schedules, repeat analysis, quality-control checks or result verification.

Who Should Take This Test?

This test may be appropriate for patients undergoing specialist assessment of suspected abnormal DHT production, androgen utilisation or 5-alpha-reductase activity. It may also be considered when a total DHT value does not adequately explain clinical findings.

A doctor may request the test during selected endocrine, reproductive or developmental evaluations or when monitoring treatment that alters DHT production. It is not generally recommended as a routine wellness, fertility, hair-loss or prostate-screening test.

The high degree of analytical specialisation means that the test should be ordered when the result is expected to answer a specific clinical question. More commonly available hormone tests may be sufficient for many patients.

Detailed Information

DHT is formed from testosterone by 5-alpha-reductase. Different enzyme forms are expressed in different tissues. Type 2 activity is important in genital tissues and the prostate, while type 1 activity is found in several tissues, including sebaceous glands.

Circulating DHT is strongly bound to SHBG. Smaller quantities are associated with albumin, and only a very small percentage circulates freely. Because binding-protein concentrations differ between individuals, two people with similar total DHT values may not have identical free DHT concentrations.

Equilibrium dialysis may be used to separate the free hormone fraction from protein-bound hormone. High-performance liquid chromatography with tandem mass spectrometry can then measure DHT at low concentrations. These specialised steps contribute to the longer reporting time and higher test cost.

Low Free DHT may occur in patients taking 5-alpha-reductase inhibitors or in those with reduced DHT production. Suspected genetic 5-alpha-reductase deficiency requires interpretation of testosterone, DHT and their relationship, sometimes following hormonal stimulation.

An elevated Free DHT result does not independently diagnose a specific disease. Possible interpretation depends on total DHT, testosterone, SHBG, medicine use, age, sex, symptoms and the laboratory method.

Free DHT is different from free testosterone. Testosterone and DHT are separate androgens, although DHT is produced from testosterone. Each test answers a different clinical question and should not be substituted without medical advice.

Reference intervals vary according to sex, age, developmental stage and analytical method. Results should be interpreted using the ranges supplied by the performing laboratory and reviewed by an endocrinologist, andrologist, urologist or another qualified specialist.