A condition characterised by underactivity of the testes (see TESTICLE) or OVARIES – the gonads. The condition may be caused by a genetically based disorder resulting in an abnormally functioning gonad (primary hypogonadism) or by a malfunctioning PITUITARY GLAND that fails to produce an adequate amount of gonadotrophin hormone (see GONADOTROPHINS) – secondary hypogonadism. Those affected may fail to develop adequately the secondary characteristics of their sex: males will have delayed puberty, erectile impotence and infertility and also develop GYNAECOMASTIA; females also have delayed puberty, infertility, and sometimes HIRSUTISM.