Effects of soya milk on reproductive hormones during puberty in male Wistar rats

Puberty is considered a critical period on development that involved sexual maturation and morphological changes. Isoflavones have been described as endocrine disruptors in male rats. Therefore, the present study attempt to evaluate the effect that daily intake of low and high doses of isoflavones exert into the hormonal regulation that take place during puberty by analyzing the levels of serum and testes steroid and pituitary hormones. 108 male pre-puberal Wistar rats (30 days old) were randomly divided into three groups; control, low and high doses of isoflavones. Experimental animals were daily dosed orally with low and high doses of a mixture of two soy isoflavones (genistein and daidzein) during 6 weeks. An EIA was performed in serum and testes homogenates for analyzing FSH, LH, P5, P4, DHEA, A4, T, DHT, SO4E1 and E2 hormone concentrations. Results revealed a decrease of an oestrogen environment in testes stimulates the secretion of FSH and LH leading to the production of androgens in the testes at the onset of puberty. Low doses of isoflavones resulted in a significant increase of testes oestrogens that consequently produced a delay on the onset of puberty; however at high doses of isoflavones the maintained oestrogenic environment in the testes prevent the stimulation of the secretion of pituitary hormones and the production of T abolishing the onset of puberty. These results clarify the hormonal mechanisms that take place on puberty and determine the effect of high and low doses of isoflavones at the onset of puberty.