Hematic levels of leptin vary in relation to numerous metabolic factors and are able to interact in perfect synchrony with the hor­mones involved in the hypothalamus-pituitary-ovarian axis during the various phases of the reproductive cycle. In general it is main­tained that the complex and multiple action mechanisms of leptin need to be clarified by further indepth research studies. It is likely that valid pharmacological applications of leptin will be found for human use although it is too premature to talk about concrete pharmacological answers and to formulate the relative complete technical protocols. In medicine the therapeutic use of leptin for humans has been reported in only a few cases. In fact human recombinant leptin has already been administered in gynecology for hypothalamic amenorrhea with precise protocols. In addition, very recent studies have provided the basis for new strate­gies to be developed concerning the use of leptin to fight multiple sclerosis At present there are considerable technical and economic problems in the production of leptin on a large scale. Most likely these problems will be overcome in the foreseeable future, and will involve new techniques related to genetics, cellular reprograming, and stem cells. In fact, new pharmacogenetic research has provided encouraging results for the production in industrial quantities of a more effective and fail-proof leptin. Even considering that norms have not yet been proposed for pharmacological interventions with leptin for use directly on humans, in our work we have studied by immunohistochemistry methods the distribution of leptin and its receptor (Ob-R) in the ovaries of the female dog as a biological model, in the pre- and postpubertal phases and in other phases of the ovarian cycle. Given the hypoth­esis that the information obtained from immunohistochemical localization of the hormone and its receptor in various ovarian struc­tures is transferable to humans, it could be useful to define therapeutic protocols based on the effective role of leptin and its recep­tor in folliculogenesis.