The effects of iron and selenium in iodine containing multivitamins on thyroid related compounds during pregnancy in Sweden: a randomized placebo cotrolled trial

• Multivitamins with iodine are advocated to pregnant women to avoid iodine deficiency, as iodine may be beneficial for brain development in the child. Multivitamins also contain iron and selenium that may affect thyroid hormone metabolism. Iron is included in the tyreoperoxidase enzyme promoting the coupling of iodine to thyroglobulin (Tg) and selenium is incorporated in deiodinases that regulates levels of thyroxine (T4) and triiodothyronine (T3). There is no previous studies on the effects of iodine containing multivitamins on iron and selenium levels in pregnant women and the relation to thyroid hormone levels. This was a randomized, double-blinded controlled trial of 200 pregnant women, who were randomized to multivitamins containing 150 lg iodine, 12 mg iron and 50 lg selenium/day or multivitamins without iodine, iron and selenium in pregnancy week 7–12 until delivery, besides iron supplements on usual routines. Thyroid hormones, Tg, selenium (ref 0.7– 1.2 lmol/L) and iron measurements (ferritin (ref 15–150 mg/L), transferrin saturation (ref 0.1–0.5)) were collected in the third trimester. Urinary iodine concentration confirmed mild ID in the control group with a Tg increase. In the third trimester, 139 patients were left for sampling. In the active group (n = 67) median (interquartile range (IQR)) selenium levels were 0.72 (0.16) vs 0.61 (0.14) in the control group (n = 72), p < 0.001. Low selenium values were noted in 70.0% of participants and it was more common in the control group (81.9%), p < 0.001. Median (IQR) Tg levels was higher in those with low selenium 30.0 (30.5) than in those with normal selenium 20.5 (21.5), p = 0.037. Thyroid hormones did not differ between active/control groups or low/normal selenium groups, but FT3/FT4 ratio was higher in the low selenium group than in the normal selenium group (0.35 (0.08) vs 0.33 (0.08)), p= 0.025. Ferritin in the active group was 22.0 (21.0) and 20.0 (21.5) in the control group, p = 0.393 and transferrin saturation 0.20 (0.11) and 0.18 (0.18), p = 0.802, respectively. Multivitamins used during pregnancy to increase iodine levels also increase selenium levels where effects on thyroid metabolism needs further evaluation.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Allmänmedicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- General Practice (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine (hsv//eng)

Publication and Content Type

vet (subject category)

kon (subject category)