The impact and efficiency of an iodine control program can be determined by:

Epidemic assessment is absolutely necessary before initiation of any iodination programme and is also required for the surveillance of goitre control programme. Among all the indicators set up for the assessment, the most sensitive is the neonatal hypothyroidism in order to analyze the environmental iodine deficiency. Compared to the serum levels of T3, T4 is a more sensitive indicator. Thus neonatal thyroxine levels is the appropriate answer. Prevalence of goitre is an indicator though it has not been specified for children aged between 12 - 18 years and pregnant females. The iodine levels in urine (not specified as that of pregnant women) are useful in surveillance purposes. Ref: Park's Textbook of Preventive and Social Medicine 19th Edition; Pages 493 - 494; 510 - 511