Association between heavy metals and endometriosis; results of a preliminary study

Abstract

OBJECTIVE: To determine the association between heavy metal concentrations in whole blood and ectopic endometrial tissue in endometriosis. DESIGN, SETTING, METHODS: A case-control study was conducted in a tertiary care setting to compare heavy metal concentrations in whole blood among those with and without endometriosis. Endometriosis was confirmed by laparoscopy or laparotomy (n=14). There were 11 age matched controls who had no evidence of the disease. Informed written consent was obtained pre-operatively. Blood samples were collected from all participants. Ectopic endometrial tissue samples were obtained from 10 cases by a single surgeon. After measuring the wet weight, whole blood samples and ectopic endometrial tissues were digested with supra pure 65% HNO3 and analyzed for heavy metals by the Total Reflection X-ray Fluorescence (TXRF) technique. Means of the log transformed metal levels were compared using t-tests. RESULTS: Mean (+SD) blood levels of nickel in the cases (2.19±0.45 PPB) was significantly higher than in the controls (0.65±0.14 PPB, p=0.029). The mean (+SD) lead levels in the cases (21.85±1.99 PPB) and controls (17.85 ±1.5 PPB) were similar (p=0.378). Tissue samples had higher mean (+SD) levels of nickel (9.3±15.31 PPB) and lead (18.16 ±1.58 PPB) as compared to blood levels of nickel (0.502±0.406 PPB) and lead (66.60+10.37 PPB), respectively, which were statistically significant {p<0.05 for both nickel and lead). CONCLUSIONS: Nickel is known to exert oestrogenic effects. Patients with endometriosis had higher levels of nickel; there is evidence that nickel accumulates in endometrial tissues. Further studies with a larger sample size are needed to determine if nickel is an aetiological factor of the disease in our population.