The association between organochlorine and thyroid hormone levels in cord serum: a study from northern Thailand.

It is now known that many organochlorines (OCs) act as endocrine disruptors, causing harmful effects on wildlife and humans. Several field and laboratory animal studies have reported that OCs cause adverse effects on thyroid hormone status. However, data regarding their effects on thyroid hormone status in humans are inconclusive. Because a developing fetus is especially sensitive to hormonal disruption by exposure to OCs, the adverse health effects on infants are of concern. The present study aimed to investigate the association between OC levels in maternal and cord serum, and the association between OC and thyroid hormone levels in cord serum. The study was performed with 39 mother-infant pairs from Mae Rim District of Chiang Mai Province, northern Thailand, who had normal delivery and full term gestation. Maternal blood was collected for measuring OCs and total lipids. Umbilical cord blood was collected for measuring OCs, total lipids, and thyroid hormones, including total thyroxine (TT(4)), free thyroxine (FT(4)), and thyroid stimulating hormone (TSH). 1,1-dichloro-2,2-di(4-chlorophenyl)ethylene (p,p'-DDE) had the highest level in all serum samples with a geometric mean of 1,191 ng/g lipids in maternal serum and 742 ng/g lipids in cord serum. The second highest level was that for 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane (p,p'-DDT), followed by 1,1-dichloro-2,2-di(4-chlorophenyl)ethane (p,p'-DDD). Levels of p,p'-DDE, p,p'-DDT, p,p'-DDD, and dieldrin in maternal serum were positively associated with levels in cord serum (r = 0.86, 0.77, 0.66, and 0.60, respectively; P<0.001). The important findings were that cord serum TT(4) levels were negatively associated with cord serum levels of p,p'-DDE (r = -0.37, P = 0.024), p,p'-DDT.3 (r = -0.33, P = 0.048), and 1,1-dichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethylene (o,p'-DDE) (r = -0.76, P = 0.019). These results therefore suggest that exposure to DDT and its metabolites during fetal development may cause some effects on thyroid hormonal status in infants.

Plasma levels of DDT and their association with reproductive hormones in adult men from northern Thailand.

Historically, dichlorodiphenyltrichloroethane (DDT) was used in northern Thailand for malaria control and farming purposes. Several studies have investigated its effects on end points of adverse reproductive health outcomes. However, the few previous studies investigated hormonal effects in men and available data are inconclusive. The authors aimed to explore the main hypothesis that plasma DDT levels in adult men were associated with reproductive hormone levels. A cross-sectional study was performed of 97 adult men living in a highland village named Mae Sa Mai, 35 km north of Chiang Mai, Thailand. Venous blood samples were collected for measuring plasma levels of DDT and its metabolites and reproductive hormones, including 17beta-estradiol (E2), testosterone, luteinizing hormone (LH), and follicle stimulating hormone (FSH). 1,1-Dichloro-2,2-di(4-chlorophenyl)ethylene (p,p'-DDE) and 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane (p,p'-DDT) were detected in all plasma samples. p,p'-DDE had the highest level with a median of 4057.7 ng/g lipids and a relatively higher level compared with most other studies. Plasma p,p'-DDT levels were positively associated with years of residence (beta+SE=0.472+0.208, P=0.028) and years of DDT usage for farming (beta+SE=0.177+0.084, P=0.04). The remarkable findings were the negative association of plasma E2 levels with plasma p,p'-DDE levels (beta+SE=-7.093+2.899, P=0.016) and the positive association with plasma 1,1-dichloro-2-(2-chlorophenyl)-2-(4-chlorophynyl)ethylene (o,p'-DDE) levels (beta+SE=16.381+5.596, P=0.008) after adjusting for age and body mass index (BMI). However, these associations were rather weak. Our results suggest that these associations may reflect their different mechanisms of hormonal activities and they would be warrant further detail investigations.