Endocrine Abstracts

Introduction

Twenty-four years after implementing the national salt iodization programme in Poland in 1997, the country is considered as adequate iodine supply. However, most reports do not take into consideration pregnant or lactating females. Additional intake of 150–200 µg KI per day, independently on levothyroxine (LT4) treatment, is a recommended dose for pregnancy and lactation due to Polish endocrinological guidelines. The study aim was to evaluate iodine supply in the group of pregnancies and relate the results to maternal thyroid parameters.

Material & methods

95 mother-child pairs (healthy, hypothyroid and euthyroid with autoimmune thyroiditis with or without LT4 treatment) were recruited at planned admission to the obstetric ward of tertiary reference gynaecological hospital. The venous blood serum was obtained from mothers before delivery, where thyrotropin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) and antibodies against thyroid peroxidase (a-TPO) and thyroglobulin (a-Tg) were measured by ECLIA. A single random urine sample was obtained from mothers to measure ioduria (UIC) by a validated ion-pair HPLC-UV method. Additionally, urine creatinine was measured by ELISA and iodine/creatinine ratio (UIC/Cr) was calculated.

Results

71% declared iodine supplementation intake in dose 150–200 mg/daily. The median UIC was 105 µg/l (Q25-Q75, 69–171). According to WHO 68% were iodine-deficient < 150 µg/l (including 10% with deficits < 50 µg/l), 22% were adequately supplied (150–249 µg/l), 9% had more than adequate supplies (250–499 µg/l) and 1 patient had excessive supply (> 500 µg/l) on concomitant high-dose LT4 treatment. The median UIC/Cr ratio was borderline adequate 151 µg/g (Q25-Q75, 64–282), but the higher percentage of patients (41%) had results < 100 g/l and 25% between 100 and 200 g/l. Additionally, in the group not-treated with LT4, women who supplemented iodine had higher fT3 (4.3 vs 3.7, P = 0.03) pmol/l.

Conclusions

Despite recommendations one-third of recruited women did not supplement iodine during pregnancy. Most females were iodine-deficient independently from iodine supplementation. Iodine intake may improve maternal thyroid function. During the construction of future guidelines, an increase of the recommended dose of iodine supplementation in pregnancy should be considered, taking into consideration concomitant LT4 treatment.