Renal and reproductive effects

IGFs (in particular IGF-1 and also IGFBP-1) are localized within various areas of the kidney. Direct infusion of IGF-1 influences (usually enhances) renal function by a number of means, including promoting  

GH deficiency often leads to delayed puberty. This condition often responds to exogenous GH administration. IGFs, as well as their receptors and binding proteins, are widespreadly expressed in the male and female reproductive tissue. Thus, IGFs are believed to affect reproductive function by both (GH-stimulated) endocrine action and via paracrine- and autocrine-based activity. 

In the human female, IGF-1 is expressed by follicular theca cells, while IGF-2 is synthesized by granulosa cells (Chapter 8). The IGF-1 and -2 receptors are widely expressed in ovarian tissue, and synthesis of both growth factors and their receptors are influenced by circulating gonadotrophin levels. IGF-1 exerts a direct mitogenic effect on human granulosa cells, and promotes increased androgen and oestradiol synthesis by these cells. IGF-1 also promotes increased expression of FSH and LH receptors in ovarian tissue. 

In the male, IGF-1 is synthesized by the Sertoli and Leydig cells of the testes. It also stimulates testosterone production by the Leydig cells, and promotes growth and maintenance of various additional testis cell types. 

IGFs thus play an essential role in many facets of reproductive function. Traditionally, therapeutic intervention in reproductive disorders at a molecular level has relied almost exclusively upon administration of gonadotrophins or LHRH (luteinizing hormone releasing hormone Chapter 8). Because of their widespread reproductive effects, IGFs may yet prove a valuable adjunct therapy in some instances. 

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