In humans, hyperprolactinaemia is associated with a marked reduction in both the frequency and amplitude of LH pulses (Bohnet et al. 1976, Matsuzaki et al. 1994) indicative of a change in GnRH pulses, and the suppression of LH pulsatility can be reversed by reducing serum prolactin concentrations to normal (Moult et al. 1982). The gene discussed is PRL; the disease is Increased circulating prolactin concentration.