Paracrine/autocrine control of female reproduction

Neuropeptides, growth factors and cytokines are expressed in reproductive o rgans and tissues, where they interact with afferent endocrine messages to modulate cell proliferation and differentiation, local hormone secretion an d vascular function. These events regulate complex processes such as gonado tropin pulsatility, ovulation, implantation and parturition. During reproductive life, a number of neuropeptides produced within the hyp othalamus play a modulatory role irt the control of gonadotropin-releasing hormone (GnRH) release, hence characterizing a hypothalamic paracrine syste m. The pituitary gland is a source and target of inhibin-related proteins, and these typical 'gonadal' products, once secreted by the pituitary cells, acquire the function of paracrine modulators of follicle-stimulating hormo ne (FSH) secretion. In the ovary, the effect of gonadotropins is locally mo dulated by growth factors acting in an autocrine/paracrine manner, although their precise rot in folliculogenesis remains uncertain. Numerous local fa ctors ave involved in the control of endometrial growth, differentiation, r eceptivity and menstruation. Alterations in the paracrine endometrial syste m may underlie pathological processes such as infertility or endometrial ne oplasia. The human placenta and its related membranes produce cytokines, ho rmones and growth factors that participate in the control of gestational de velopment as well as in the maternal-fetal adaptation to gestational diseas es. There is increasing evidence that paracrine signaling plays a fundamental r ole in all spheres of female reproductive function, and future research wil l concentrate on clarifying which of these local mechanisms play a decisive role in both physiology and disease, thus giving vise to new therapeutic s trategies.