Endocrine Abstracts

Perchlorate (CLO4) and thiocyanate (SCN) are environmental pollutants which inhibit iodine uptake into thyrocytes. Contamination has been found in water, milk and some foods and originates from cigarettes, nitrogen fertilisers, fireworks and rocket fuels. These pollutants may potentially compound iodine deficiency and partly explain the four-fold rise in congenital hypothyroidism described in NI, Ireland and other Western countries over the last 40 years. A cohort of 240 mothers provided urine samples for storage each trimester and postpartum with a subset of 60 providing an offspring sample (6-24 weeks). Mothers were iodine deficient while babies were iodine replete, as previously reported. Maternal median perchlorate levels across trimesters and postpartum were 3.6, 4.1, 3.3, 3.8 mg/lrespectively and 1.9 mg/lin offspring (detectable in 65% babies). Maternal median thiocyanate levels were 353, 709, 572, 751 mg/lrespectively and 136 mg/lin offspring (detectable 100% babies). Smoking was associated with four-fold higher levels in maternal thiocyanate in second trimester vs non-smokers (2970 vs 657 mg/l, P = 2.5 × 10⁻¹⁶). Contemporaneous water samples from across island of Ireland had unmeasurable levels of CLO 4 and SCN (<0.05 and <0.5 mg/lrespectively). To our knowledge this is the first European cohort shown to have evidence of thyroid hormone synthesis blocker contamination in babies. Mothers were iodine deficient in each trimester. Results are similar to a baby cohort from Boston USA. However, in the Boston cohort mothers were iodine replete and this may provide some protection not afforded to Ireland and UK which have no iodine fortification programmes.