<prompt> Masculine or feminine features most directly depend onAmygdalaGenetic makeupHypothalamic outflowSerum testosterone levels  <response>: Ans. d Serum testosterone levels. Ref. Ganong, Physiology, 21st ed., 420TestosteroneSource Testis Leydig cells, adrenalPotency DHT testosterone androstenedioneTargets Skin, prostate, seminal vesicles, epididymis, liver MH-2000Functions1.Differentiation of wolffian duct system into internal gonadal structures. 2.Secondary sexual characteristics and growth spurt during puberty. 3.Required normal spermatogenesis. 4.Anabolic effects on muscle size, RBC production 5.Increases libido Testosterone is converted to DHT by the enzyme 5 a-reductase, which is inhibited by finasteride. FunctionsAndrogen binding protein ABPEnsures that testosterone in seminifierous tubule is high.Inhibininhibits FSHTestosteroneDifferentiates male genitalia, has anabolic effects on protein metabolism, maintains gametogenesis, maintains libido, inhibits GnRH, and fuses epiphyseal plates in bone.FSHSertoli cells function sperm production spermiogenesisLHLeydig cell 