This chapter reviews methods to integrate hormones into theory and research in social and personality psychology. The advantages of hormones include identifying possible mechanisms that link the social environment to better physical and mental health; disadvantages include difficult psychological inference and multiple sources of variability. Three biological systems are reviewed, including the hypothalamic–pituitary axis, the hypothalamic–pituitary–gonadal axis, and neuropeptides, and six hormones are examined in depth. Following this review is a summary of the psychological and affective states most commonly linked to these hormones. The chapter then explores best measurement practices, important covariates, and temporal factors, including basal states, diurnal fluctuations, and reactivity, followed by how to measure, analyze, and interpret hormone data. It concludes with topics from social and personality psychology that profitably leverage hormonal data to advance theoretical and empirical research, including intergroup interactions, power and status, values, and emotions and affect.

The male reproductive system is a complex network of central nervous system circuits and internal and external pelvic organs. The hypothalamic–pituitary–gonadal (HPG) axis leads to reproductive tract formation and development during embryogenesis, sexual maturation at puberty, and testosterone and sperm production by the testis as an adult. Spermatogenesis is regulated by pulsatile secretions of GnRH, LH, and FSH and feedback regulation on the HPG axis. Immotile spermatozoa are produced within the seminiferous tubules of the testis. During transport through the epididymis, sperm undergo the maturation processes to induce motility and subsequent fertility. Sperm are transported through the ejaculatory ducts and into the urethra during ejaculation, combining with the seminal fluid that provides a nutrient-rich environment, assists in sperm motility, and suppresses the immune response in the female reproductive tract.