Alterations in liver and thyroid function testsin patients with lead poisoning

Exposure to lead, damages vital organs and is now a global concern. Toxic effects of lead on the liver and thyroid gland have been mentioned previously, sometimes with conflicting results. Therefore, the present study aimed to assess changes in liver and thyroid function tests in patients with lead poisoning.

This case-control study was performed on 100 patients with clinical evidence of lead poisoning who were referred to Loghman-e-Hakim hospital in Tehran from April to December 2018. Also, another 100 participants with the matched sex and age, a history of opium use, and exposure to lead or non-work-related metals, and with normal lead levels, were considered as a control group. Demographic information was collected by a trained researcher by reviewing hospital records or interviewing participants. To monitor lead levels in the control group, 5 ml of venous blood was collected from the antecubital vein at 7 to 8 am in sterile tubes containing EDTA as an anticoagulant. Serum lead levels were assessed by GBC Avanta atomic absorption spectrophotometer. Values in the two groups were compared. SPSS version 16 (SPSS Inc. Chicago, Il, The USA) was used for data analysis. A P-value below 0.05 was considered statistically significant.

The mean level of serum lead in case and control groups were 63.0±12.4 μg/dL and 6.0±2.1 μg/dL, respectively with a statistically significant difference (p<0.001). However, Alkaline phosphatase (ALKp), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) enzymes were significantly higher in cases compared to controls (p<0.001). The thyroid-stimulating hormone in patients with lead poisoning (0.3±0.04 MIU/L) was significantly lower than those in the control group (2.5±1.23) (P=0.04).

Lead poisoning could potentially damage liver function and elevate liver enzymes. Moreover, it can also affect the levels of TSH and levothyroxine. Understanding the exact mechanisms might help to control The hepatotoxic effects of lead in patients. Also, knowing the pattern of elevated liver enzymes and thyroid hormones changes might help discriminate lead poisoning with other differential diagnoses.