The ovary.
The functions of the ovary can be described as a storehouse for oocytes as well as a factory to produce mature oocytes at the appropriate time for fertilization and hormones at the appropriate time and in the appropriate quantities to assure fertility. A complex multiple-job specification such as this requires control processes which allow all facets to operate successfully at the same time, and in a co-ordinated manner. This can only be achieved by hypothesizing control at several levels, namely, externally via gonadotrophins (and perhaps GH and prolactin), and internally via local regulators, where the local regulators control the gonadotrophin-independent processes and fine tune the gonadotrophin-dependent processes. The available evidence is consistent with a role for local regulators in the control of follicular and luteal function in the ovary. In most cases, however, the nature of the local regulator involved in a particular process is not known. On the other hand, the list of candidates continues to increase (see Table 1). A priority for future research will be to firmly establish many of these substances as local regulators and to understand how and when they exert their actions, particularly in vivo. A particularly complex question concerns the potential interaction between the local regulators which have either similar or opposing actions. The clinical significance of local regulation in the ovary is yet to be fully appreciated. The addition of GH to gonadotrophin therapy for ovulation induction (Homburg et al, 1988) is the first example of the application of findings from basic research on local regulators in the ovary. It may be that clinical syndromes such as resistant ovary syndrome, polycystic ovarian disease and luteinized unruptured follicle have some perturbation of local regulator production or action, which, if defined, would underline the importance of local regulation and could offer a means of treatment.