Knowledge of the effect of differences in iodine intake levels on public health in areas with no endemic goiter is limited. Groups at risk when iodine intake is relatively low are pregnant and lactating women and their newborns. A prospective randomized study was performed to evaluate the effect of iodine supplementation in an area where the median daily iodine excretion in urine is around 50 micrograms. Fifty-four normal pregnant women were randomized to be controls or to receive 200 micrograms iodine/day from weeks 17-18 of pregnancy until 12 months after delivery. In the control group, serum TSH, serum thyroglobulin (Tg), and thyroid size showed significant increases during pregnancy. These variations were ameliorated by iodine supplementation. Iodine did not induce significant variations in serum T4, T3, or free T4. Cord blood Tg was much lower when the mother had received iodine, whereas TSH, T4, T3, and free T4 levels were unaltered. The results suggest that a relatively low iodine intake during pregnancy leads to thyroidal stress, with increases in Tg release and thyroid size. However, the thyroid gland is able to adapt and keep thyroid hormones in the mother and the child normal, at least under normal circumstances, as evaluated in the present study. It is not known whether this stress is sufficient to be of importance for late development of autonomous thyroid growth and function.

In the Randers area of Denmark urinary iodine excretion (which reflects iodine intake) was found to be much lower than recommended intake levels, both in women in late pregnancy [52(23-118) micrograms iodine/g creatinine, median, range, n = 20] and in non-pregnant controls [42(23-71), n = 20]. Serum thyroglobulin which is high in iodine deficiency was 32.5 micrograms/l (median) (range 10.5-78.0) in the control women and considerably higher in the pregnant women [67.0 micrograms/l (9.0-385)]. This increase was probably due to the extra iodine requirement of pregnancy which was not satisfied with an adequate increase in iodine intake. The results may suggest that pregnant women in this area should receive iodine supplementation and that a general program of iodine supplementation should be considered.

In order to obtain direct information about vascular changes associated with pre-eclampsia, the morphological and functional characteristics of isolated omental resistance vessels from 11 women with pre-eclampsia, 10 normotensive pregnant women and eight normotensive non-pregnant women were determined. In vessels from the women with pre-eclampsia, the ratio of media thickness to lumen diameter was increased, compared with that in vessels from the other two groups. The vessels from the women with pre-eclampsia had an increased responsiveness to angiotensin II and a decreased rate of relaxation, but only when compared with the vessels from the normotensive pregnant women. However, no difference in responsiveness to noradrenaline was found between any of the groups. The angiotensin II responsiveness of the vessels from the women with pre-eclampsia and from the non-pregnant women were similar, suggesting that pre-eclampsia is associated with an absence of the change in vascular function which normally occurs during pregnancy. The study provides direct evidence for an involvement of vascular abnormalities in the pathogenesis of pre-eclampsia.

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Iodine requirements are increased during pregnancy and lactation and adequate iodine intake is important for normal brain development of the fetus/newborn child. The aim of the present study was to evaluate the extent to which this increase in iodine requirement is met in pregnant women living in various regions of Denmark. One hundred and fifty-two healthy pregnant women admitted to five different Danish departments of obstetrics participated in the study. Iodine status was evaluated by measurement of iodine in spot urine at day five after delivery and by careful history of the intake of iodine containing vitamin/mineral tablets. Approximately one third of the women had received tablets containing iodine. In women who had not received iodine supplementation urinary iodine was low with a median value of 39.7 micrograms/g creatinine (Aalborg 28, Randers 33, Ringkøbing 34, Arhus 43 and Copenhagen 62 micrograms/g creatinine). These values are far below internationally recommended levels. The consequences remain to be evaluated and no firm recommendations can be given. It seems reasonable, however, to recommend a high intake of food containing iodine (e.g. milk products) during pregnancy and lactation. Since nearly all the women took some kind of vitamin/mineral supplementation it could be considered to advocate intake of vitamin/mineral tablets containing iodine.