Hormones and Hormonal Target Cells in the Testis*

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Abstract
Studies over the last few years have greatly increased our knowledge about target cells for sex hormones and gonadotropins in the testis. A diagram illustrating our present state of knowledge is given in Fig. 1. LH is the principle stimulus of testosterone secretion by the Leydig cells. Direct effects of estrogens and androgens on these cells might modulate the response to LH. Androgens are apparently influencing the differentiation and the contractility of peritubular cells. FSH is the principle stimulus for Sertoli cell secretory function before puberty, although androgens are acting synergistically with FSH. After puberty, androgens alone are capable of maintaining on optimal secretory function of the Sertoli cells. In addition to normal secretory activity of the Sertoli cells, direct stimulation of the germ cells by androgens is needed in order maintain spermatogenesis.Recent literature on the presence of target cells in the testis for sex hormones and gonadotropins is reviewed. The current state of knowledge is summarized in a diagram. It appears that luteinizing hormone (LH) is the primary stimulus for testosterone secretion by the Leydig cells. These cells also seem to have some affinity for estrogens and androgens, which may modulate their response to LH. The differentiation and contractility of peritubular cells appears to be influenced by androgens. Before puberty, follicle stimulating hormone is the primary stimulus for Sertoli cell secretory function, although androgens also participate synergistically. Following puberty, androgens are capable of maintaining optimal Sertoli cell secretory function by themselves. Androgen stimulation of germ cells is also required for normal spermatogenesis.