To study the effects of sleep deprivation on the pituitary-testis axis physiology, we measured the circulating levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), testosterone (T), androstanedione (A), dihydrotestosterone (DHT), estradiol (E2), and cortisol (C) in eight healthy men as follows: phase I (control), phase II (24-h restless period), phase III (48-h restless period), and phase IV (24-h recovery period). All samples were taken at 8:00 a.m. There was a significant decrease of T, A, DHT, and E2 in phase II but no decrease in FHS, LH, PRL, or C. In phase III there was no further decrease in any androgen, although E2 decreased along with the increase of PRL. In phase IV E2 and PRL tended to return to baseline values, and the androgens were very similar to the controls. FHS, LH, and C showed no change under the effects of phase III. These data extend the adaptive androgenic response and the association of the role of E2 and PRL to restricted or disturbed sleep in men.