Iodine deficiency in ambulatory participants at a Sydney teaching hospital: is Australia truly iodine replete?

Objective: To assess iodine status in four separate groups - pregnant women, postpartum women, patients with diabetes mellitus and volunteers. Design and setting: Prospective cross-sectional study at a tertiary referral hospital in Sydney. Participants: 81 pregnant women attending a "high risk" obstetric clinic; 26 of these same women who attended three months postpartum; 135 consecutive patients with diabetes mellitus attending the diabetes clinic for an annual complications screen; and 19 volunteers. There were no exclusion criteria. Methods: Spot urine samples were obtained, and urinary iodine was measured by inductively coupled plasma mass spectrometer. Outcome measures: iodine status based on urinary iodine concentration categorised as normal (>100 mu g/L), mild deficiency (51-100 mu g/L) and moderate to severe deficiency (<50 mu g/L). Results: Moderate to severe iodine deficiency was found in 16 pregnant women (19.8%), five postpartum women (19.2%), 46 patients with diabetes (34.1%) and five volunteers (26.3%). Mild iodine deficiency was found in an additional 24 pregnant women (29.6%), nine postpartum women (34.6%), 51 patients with diabetes (37.8%) and 9 normal volunteers (47.4%). Median urinary iodine concentration was 104 mu g/L in pregnant women, 79 mu g/L in postpartum women, 65 mu g/L in patients with diabetes mellitus and 64 mu g/L in volunteers. Conclusions: The high frequency of iodine deficiency found in our participants suggests that dietary sources of iodine in this country may no longer be sufficient. Further population studies are required.