APPLICATION: Usually only ordered as part of a hCG stimulation test in the investigation of ambiguous genitalia. Dihydrotestosterone (DHT) is produced from testosterone by the 5-alpha-reductase enzyme. The testosterone/DHT ratio is measured. The measurement of dihydrotestosterone is only indicated for the investigation of disorders of sexual differentiation and the monitoring of 5 alpha-reductase inhibitor therapy. INTERPRETATION: DHT is the active form of testosterone in many tissues. I n 5 alpha-reductase deficiency, the testes can produce testosterone but this cannot be converted to DHT.
