Boron and Steroid Hormones in Rats

In rats, boron intake has a marked effect on the plasma testosterone concentration. As the intake of boron increased from 2 to 25 mg, plasma testosterone concentrations tended to decrease, and the response in plasma was paralleled by a decrease in the testosterone concentration in the testes 

From the studies described above and those reported by others, as reviewed by Nielsen (1991,1997, 2000, 2008), boron is capable of influencing steroid hormone metabolism however, the specific conditions that control the nature (and direction) of the response remain to be determined. 

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