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Web Topic 5.3: Coupling between Androgen Secretion and Spermatogenesis

[Referenced on textbook p. 129]

You might imagine that LH and FSH would each be independently responsible for activating one of the two testicular functions, hormone secretion or spermatogenesis. But that assumption would ignore the purpose of the entire system. From a reproductive standpoint, hormone secretion and spermatogenesis should be coupled. There is no point having the testes secrete high levels of testosterone, with all the consequences for a man’s physical and psychological state that we’ll describe later, unless he is producing sperm—and vice versa. To achieve this coupling, LH and FSH interact at the level of the testicular Leydig and Sertoli cells (see Figure 1). Leydig cells express LH receptors, and they secrete testosterone (and estrogen) when stimulated by LH. Sertoli cells, on the other hand, express receptors for both FSH and androgens, and each hormone stimulates the Sertoli cell to increase the expression of receptors for the other hormone. (In other words, testosterone stimulates the expression of FSH receptors, and FSH stimulates the expression of androgen receptors.) This arrangement results in synergism, or cooperative action, between the two hormones, so that Sertoli cells activate high levels of sperm production only when both androgens and FSH are present.

Figure 1  Influence of gonadotropins on the testis.