Figure 2. Specific actions of testosterone (T) and 5α-dihydrotestosterone (DHT). A) Testosterone is synthesized in the testis under the control of luteinizing hormone (LH) from the pituitary. After entering target cells in the hypothalamus, pituitary, testis, and Wolffian duct, T binds to the androgen receptor (AR) and the T-AR complex binds to specific DNA sequences and regulates gene transcription, which can result in negative feedback regulation of gonadotrophin synthesis and secretion, in initiation and regulation of spermatogenesis, and in differentiation and development of Wolffian ducts. B) T is synthesized in the testis under the control of LH, enters target cells in urogenital sinus, urogenital tubercle, and several other androgen target tissues and is metabolized to DHT by the enzyme 5α-reductase type 2. DHT binds directly to the AR and the DHT-AR complex interacts with specific DNA sequences and regulates gene transcription resulting in differentiation and development of the prostate, the external genitalia, and during puberty several secondary male sex characteristics.