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DISCUSSION

Result of Soy Formula Feeding in Marmoset

Monkeys:

y Suppression of the neonatal testosterone surge

y

Increased Leydig Cell numbery No adverse effects on pubertal progression or fertility

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Dietary Phytoestrogens on Rats

y Decrease in fertility

y Changes in the expression patterns of ER and AR in

the epididymis

y No change in the conventional semen quality

parameters

y Decrease circulating testosterone level

y NO effect on testicular weight or spermatogenesis in

adult rats

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Phytoestrogen-rich Diet on Rabbits

y Increased Libido

y Improved ALL conventional semen quality

parameters

Phytoestrogen-rich Diet on Macaques

y No changes in testicular weight

y No change in semen quality parameters

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Sheeps feeding on Phytoestrogen-rich pasteurs

y Intact Males do not show evidence of reproductive

morbidity

y Castrated Males present development of mammary

glands, lactation and squamous metaplasia of the

prostate and other accessory glands

y Enlargement of Cowper·s glands

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The lack of consistent results across species

suggest the possibility of species-specific

susceptibility and highlights the importance of 

conducting further studies in humans.

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2 arguments raised against the possibility that

phytoestrogens have deleterious effects on male

fertility:

y 1.T

he low in vitro affinity of individualphytoestrogens to ER, 100-1000x lower than

estradiol.

- makes it unlikely that phytoestrogens can exert

significant estrogenic activity to result in major altered

reproductive function.

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Phytoestrogens can bind membrane ERs with

greater affinity than they bind nuclear receptors Induce transcriptional activity to the same extent estradiol

does.

In Mouse Sperm (conc 100-1000x lower than

estradiol):

y Induce capacitation

y Premature acrosome reaction

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Human sperm appears to be MORE sensitive

than mouse sperm to actions of specific

isoflavones.