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Abstract

Thyroid function tests (serum levels of thyroxine-T4, triiodothyronine-T3 and thyroid stimulating hormone-TSH) were performed in fifty-eight men (mean age: 31.7 +/- 10.6 years; mean duration of lead exposure: 156.9 +/- 122.7 months). These subjects were exposed to lead either as petrol pump workers or automobile mechanics. The mean whole blood lead (Pb-B) levels were 2.49 +/- 0.45 micromole/l (51.90 +/- 9.40 microg/dl) in the lead exposed workers and were approximately 5 times higher than in the control (n = 35) subjects. No significant alteration was seen in their mean T3 and T4 levels as compared with the controls. Interestingly, T3 was significantly lower with the longer (210 months) exposure time in comparison with the group having shorter (29 months) exposure duration. The mean TSH levels were significantly (p < 0.01) higher in workers exposed in comparison with the control group. This rise in TSH was independent of exposure time, but it was definitely associated with the Pb-B levels. The increase being more pronounced with mean Pb-B levels of 2.66 +/- 0.2 micromole/l (55.4 +/- 4.25 microg/dl) when compared with the group having mean levels of 1.51 +/- 0.30 micromole/l (31.5 +/- 6.20 microg/dl). The rise is TSH associated with Pb-B levels was only statistical valid, however, the levels fall within the normal laboratory range. We thus conclude that the Pb-B levels of > or = 2.4 micromole/l (50 microg/dl) could enhance the pituitary release of TSH without having any significant alterations in the circulating levels of T3 and T4.

Thyroid Hormones in Relation to Lead, Mercury, and Cadmium Exposure in the National Health and Nutrition Examination Survey, 2007–2008

“…Pb exposure [mean 15 µg/dL blood Pb (BPb) level] was negatively correlated with transthyretin levels in cerebrospinal fluid samples from human patients (Zheng et al 2001). Previous studies of populations with high exposure to Pb (indicated by BPb levels of > 20 µg/dL) suggested negative associations with circulating T 4 , FT 4 , or T 3 (López et al 2000; Robins et al 1983; Singh et al 2000; Tuppurainen et al 1988); however, associations were not evident in other similar study populations (Erfurth et al 2001; Schumacher et al 1998; Siegel et al 1989). Fewer studies have investigated associations of BPb levels of < 10 µg/dL with THs.…”

Ameliorative Effect of Vitamin C on Alterations in Thyroid Hormones Concentrations Induced by Subchronic Coadministration of Chlorpyrifos and Lead in Wistar Rats

“…Although, the present study did not evaluate histological changes in the thyroid glands, Pb on its own has been shown to cause hypothyroidism either by inhibiting iodine uptake [25, 26] and to cause functional impairment of the pituitary—thyroid axis [27]. …”

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

“…The same was observed for T3; an increase [ 456 , 457 , 458 , 462 , 464 ], decrease [ 455 , 463 ] or no change [ 458 , 459 , 460 , 461 ] after cadmium exposure. Lead exposure caused an increase [ 460 , 461 , 465 , 466 , 467 ], a decrease [ 318 , 351 , 468 ] or no change [ 423 , 454 , 457 , 458 , 459 , 469 , 470 , 471 , 472 , 473 , 474 , 475 ] in TSH levels. Likewise, an increase [ 458 , 468 , 476 , 477 ], a decrease [ 318 , 458 , 465 , 470 , 473 , 478 ] or no change [ 351 , 423 , 457 , 459 , 460 , 461 , 465 , 466 , 469 , 471 , 472 , 474 ...…”