How safe is neem extract with respect to thyroid function in male mice?

In this investigation we attempted to find out the hitherto unstudied adver se effects of neem (Azardirachta indica) leaf extract on the thyroid functi on of male mice. Neem leaf extract was orally administered in two different doses (40 mg and 100 mg kg(-1) day(-1) for 20 days). The extract exhibited differential effects. While the higher dose decreased serum tri-iodothyoni ne (T-3) and increased serum thyroxine (T-4) concentrations, no significant alterations of levels were observed in the lower dose group, indicating th at the high concentrations of neem extract can be inhibitory to thyroid fun ction, particularly in the conversion of T-4 to T-3, the major source of T- 3 generation. A concomitant increase in hepatic lipid peroxidation (LPO) an d a decrease in glucose-6-phosphatase (G-6-Pase) activity in the higher dos ed group also indicated the adverse effect of neem extract despite an enhan cement in the activities of two defensive enzymes, superoxide dismutase (SO D) and catalase (CAT). Thus, it appears that the higher concentration of ne em extract may not be safe with respect to thyroid function and lipid perox idation. (C) 2000 Academic Press.