H Bürgi

Adipose tissue has been shown to respond to insulin in vitro by several groups of investigators whose work has recently been reviewed by Jean- renaud (1). Martin, Renold, and Dagenais (2) pointed out the extreme sensitivity of adipose tis- sue to insulin. Renold, Sheps, and co-workers (3, 4) used as a metabolic index of serum insu- lin-like activity (ILA) the oxidation of glucose-1- C14 to C140,. Several investigators adopted their method with equally good results (5-7). Hum- bel (8) and others (9, 10) measured the glucose uptake of epididymal adipose tissue as an index of ILA, and Ball and Merrill (11) determined the net gas exchange. When the fat-pad assay is applied to the determination of ILA in human serum, several discrepancies become apparent be- tween its results and those obtained by other biological and immunological assay technics currently in use.

Thyroid function was studied for 42 days in 58 patients, 28 of whome had euthyroid goiter, after urography (diatrizoic acid), cholangiography (ioglycamic acid), and cholecystography (Naiopanoate). After urography and cholangiography short-lived increases of the serum thyroxine occurred in a few patients, but the mean thyroxine and triiodothyronine concentration did not change. By contrast, 7 days after oral cholecystography serum thyroxine had risen consistently by 22% with a concomittant rise of the free thyroxine, while triiodothyronine declined by 15%. The thyroxine metabolite 3,3',5'-triiodo-1-thyronine (reverse T3) rose by 50% and serum thyrotropin concentration doubled. After 42 days thryoxine and triiodothyronine had returned to baseline, and none of the 58 patients developed clinical hyperthyroidism. In patients with severe myxoedema kept on a constant replacement dose with 1-thyroxine NA-iopanoate produced similar changes with the exception of the rise of the serum thyroxine. The primary event after Na-iopanoate seems to be a fall of the serum triiodothyronine, which in turn augments thyrotropin and indirectly thyroxine secretion. the marked and sometimes sustained rose of serum thyroxine after cholecystography may lead to the erroneous diagnosis of hyperthyroidism.

Monitoring and evaluation are the last phases of a national iodine deficiency disorders (IDD) control program but among the most important. This paper summarizes the latest recommendations by the World Health Organization (WHO), the United Nations Children's Fund (UNICEF), and the International Council for Control of Iodine Deficiency Disorders (ICCIDD) about indicators and their normative values for monitoring the progress of IDD elimination and illustrates the successful monitoring programs in Switzerland and in China. Salt is the usual vehicle for iodine supplementation and quality control for iodine content can be assessed quantitatively by titration and qualitatively by simple test kits that can be used in the field. The most useful indicator of iodine nutrition is the median urinary iodine concentration. Thyroid size, especially by ultrasound, and neonatal thyrotropin (TSH) are also valuable. In Switzerland, access to iodized salt on a voluntary basis started in 1922. The initial level of iodization, 1.9-3.75 ppm iodine as potassium iodide (KI), was slowly increased to 15 ppm, and recently to 20 ppm, after careful epidemiologic and biologic monitoring. Elimination of IDD has been highly successful. The program costs US dollars 0.07 per year per person. In China, a national program of iodized salt (10-30 ppm) started in 1960 under the authority of the central government and rapidly expanded. National monitoring surveys have taken place every 2 years since 1993. Median urinary iodine, initially low, increased to 165 microg/L in 1995 and to 306 microg/L in 1999, prompting a decrease in the amount of iodine added to salt. The total goiter rate decreased to 20.4% in 1995 and to 8.8% in 1999. IDD can presently be considered as eliminated in China. Review of monitoring in the 128 other major countries affected by IDD shows extremely variable achievements, with evidence of IDD elimination in at least 18 additional countries. Some countries that were severely iodine deficient in the past are now exposed to iodine excess and risk its effects. Sustainable elimination of IDD is within reach and would constitute an unprecedented global success story in the field of noncommunicable diseases, but continuing vigorous action is required to attain this goal.

In certain regions of Switzerland, before prophylaxis, 0.5% of the inhabitants were cretins, almost 100% of schoolchildren had large goitres and up to 30% of young men were unfit for military service owing to a large goitre. Iodization of salt was introduced in 1922 at 3.75 mg I per kg and the iodine content was doubled twice, in 1962 and 1980, to the present 15 mg I per kg. In 1988, 92% of retail salt and 76% of all salt for human consumption (including food industry) was iodized, even though its use is voluntary. Urinary iodine excretion, previously between 18 and 64 micrograms per per day, has now risen to 150 micrograms per day. No new endemic cretins born after 1930 have been identified. Goitre disappeared rapidly in newborns and schoolchildren, more slowly in army recruits, and incompletely in elderly adults. In some Cantons (by constitution in charge of health matters and the salt monopoly) which allowed iodized salt only in 1952, disappearance of goitre lagged behind accordingly, proof that iodized salt was the cause of regression. The Swiss data provide evidence that isolated deafness, mental deficiency, and short stature, each without the other attributes of cretinism have also decreased. Adverse effects of iodized salt were minimal, possibly because the initial iodine content of salt was chosen very low. Iodization of salt has proved a highly cost-effective preventive measure in Switzerland.