The hypothalamic-pituitary-testicular (HPT) axis is an intricate network of feedforward and feedback signals that precisely controls testosterone exposure, androgenisation and spermatogenesis. A correctly functioning HPT axis is therefore critical for the general health and well-being of men, and for the continuation of the human species; whereas defects in this network causes a clinical syndrome of hypogonadism, which may be primary, secondary or functional. Sleep and circadian inputs affect the HPT axis, and these factors should be considered when assessing the diagnosis and biochemical confirmation of hypogonadism. Androgen use in the context of hypogonadism should be physiological, whereas pharmacological therapy for male hormonal contraception may eventually become an approved indication. This presentation will highlight recent examples of how understanding of sleep and network physiology can influence the physiological and pharmacological use of androgens in men.