Effect of iodized oil supplementation on thyroid hormone levels and mental performance among Orang Asli schoolchildren and pregnant mothers in an endemic goitre area in Peninsular Malaysia.

Although endemic goitre is no longer a major public health problem in Malaysia, iodine deficiency still remains a significant problem in a few remote settlements. The aim of this study was to determine the effectiveness of iodized oil intervention in the prevention of endemic goitre among the indigenous people in Malaysia. A pretest and post-test controlled trial was conducted among primary schoolchildren and pregnant mothers in Lasah, Sungai Siput and Perak. Legap Post and Yum Post were selected as the intervention areas, while Perwor Post and Poi Post were taken as controls. The variables studied included thyroid hormone concentrations, thyroid volume, urinary iodine excretions and mental performance. A baseline and two follow-up visits were conducted in both intervention and control areas. Intervention subjects were given iodized oil in the form of capsules which were taken orally (Laboratoire Guerbet, Paris, France). There was a significant increase in serum thyroxine hormone (T4) concentrations (p<0.0001) and a significant decrease in thyroid stimulating hormone (TSH) concentrations (p<0.05) in the schoolchildren following the intervention, however, pregnant mothers did not show any significant changes in T4 and TSH concentrations. Thyroid size was significantly reduced in both groups (p<0.05). Urinary iodine excretions showed a significant increase in both groups following the intervention (p<0.01). However, mental performance in schoolchildren was not affected. In conclusion, iodized oil (oral) is effective in reducing thyroid size, as well as improving the supply of iodine among schoolchildren and pregnant mothers in endemic goitre areas; however, its long-term effects need to be monitored closely. This method can be considered as an alternative while awaiting national coverage for the salt iodization program.