Long-term exposure to xenoestrogens alters some brain monoamines and both serum thyroid hormones and cortisol levels in adult male rats

The present study was designed to examine the effect of long-term treatment with the phytoestrogen soy isoflavone [(SIF); 43 mg/kg body weight/day] and/or the plastics component bisphenol-A [(BPA); 3 mg/kg body weight/day] on some monoamines in the forebrain and both serum thyroid hormones and cortisol levels of adult rats. Significant increases in serotonin (5-HT) and norepinephrine (NE) level, and significant decreases in 5-hydroxyindoleacetic acid (5-HIAA) level and 5-HIAA/5-HT ratio, were observed after treatment with SIF or BPA. Level of dopamine (DA) was increased in SIF-treated group and decreased in BPA-treated group. Activity of monoamine oxidase (MAO) was decreased in all treated groups. The level of serum thyroid hormones (fT₃ and fT₄) was increased after treatment with SIF and decreased after exposure to BPA, while cortisol level was increased in all treated groups. It may be concluded that long-term exposure to SIF or BPA disrupts monoamine levels in the forebrain of adult rats through alteration in the metabolic pathways of amines and disorders of thyroid hormones and cortisol levels.