ABSTRACT
<p><b>OBJECTIVE</b>To explore the effects of lead on the thyroid function of occupationally exposed workers.</p><p><b>METHOD</b>157 workers occupationally exposed to lead in a smelting factory were investigated. The concentration of lead in air at workshop was measured by flame atomic absorption spectrophotometry (FAAS) and the levels of blood lead (PbB) by atomic absorption spectrophotometry (AAS), zinc protoporphyrin (ZPP) by ZnPP meter, as well as the indexes of thyroid function, thyroid-stimulating hormone (TSH), triiodothyronine (T(3)), thyroxin (T(4)), free T(3) (FT(3)), and free T(4) (FT(4)) in serum by radioimmunoassay.</p><p><b>RESULTS</b>The workers with higher level of blood lead (> 2.88 micro mol/L) showed lower levels of T(3) [(1.54 +/- 0.39) nmol/L] and FT(3) [(5.50 +/- 1.26) pmol/L] than those with lower blood lead level [PbB: (1.92 approximately 2.88) micro mol/L group, T(3): (1.71 +/- 0.45) nmol/L, FT(3): (6.12 +/- 1.64) pmol/L, P < 0.05]. There was no obvious effect of length of service on thyroid hormone of exposed workers.</p><p><b>CONCLUSION</b>Higher level of blood lead may cause certain damage to thyroid function by inhibiting deiodination of T(4). No obvious relation between length of service and thyroid function was found.</p>