Effect of lead on thyroid hormones and liver enzymes in adult male rats

Introduction: Lead is a heavy metal that could be an environmental pollutant. It is a
natural metal that exists in water and soil, enters the body through digestive or
respiratory systems. The researches showed that various amounts of lead has some
effects on the endocrine glands and metabolic activities of the body. So, in this
research, we studied and compared the effects of different amounts of lead on thyroid
gland and liver enzymes in adult male rats.
Methods: 40 adult male wistar rats were studied in the from of experimental, sham
and control groups. Experimental group was in divided into three subgroups and
received lead acetate 25, 50, 100 (mg/kg) by oral rate, in fifteen days. Sham groups
received distilled water and control group received nothing. At the end of the
fifteenth day, blood samples were taken and concentrations of T3, T4, TSH, AST,
ALT and ALP were measured.
Results: The assessed results using Tukey test were studied. The findings after
statistical analysis showed that concentration of T3 hormone and enzymes of AST,
ALT by receiving various amounts of lead acetate in comparison with control
group show no significant difference, but concentration of TSH and ALP showed a
significant reduction.
Conclusion: According to above results and to findings and studies made by other
researchers, lead has an effect on thyroid hormones, causing damage to thyroid
function by inhibiting deiodination of T4. Lead decreases the activity of MAO and
acetylcholineasterase and in this way changes the pattern of releasing TSH. It
decreases the release of TSH hormone by inhibition of dopamine uptake. We may
conclude that lead has some toxic effect on thyroid function and the liver as well.