Libido , and colloquially sex drive, is a person’s overall sexual drive or desire for sexual activity. Sex drive is determined by biological, psychological, and social factors. Biologically, levels of hormones such as testosterone are believed to affect sex drive; social factors, such as work and family, also have an impact; as do internal psychological factors, like personality and stress. Sex drive may be affected by medical conditions, medications, lifestyle and relationship issues. A person who has extremely frequent or a suddenly increased sex drive may be experiencing hypersexuality, or puberty in which the body builds up chemicals and causes a higher sex drive. Asexual people may lack any sexual desires. A person may have a desire for sex, but not have the opportunity to act on that desire, or may on personal, moral or religious reasons refrain from acting on the urge. Psychologically, a person’s urge can be repressed or sublimated. On the other hand, a person can engage in sexual activity without an actual desire for it. Multiple factors affect human sex drive, including stress, illness, pregnancy, and others. Sexual desires are often an important factor in the formation and maintenance of intimate relationships in both men and women, and a lack or loss of sexual desire can adversely affect relationships. Changes in the sexual desires of either partner in a sexual relationship, if sustained and unresolved, may cause problems in the relationship. The infidelity of a partner may be an indication that a partner’s changing sexual desires can no longer be satisfied within the current relationship. Problems can arise from disparity of sexual desires between partners, or poor communication between partners of sexual needs and preferences.