Clinical Pearls:
- The study findings show that prevalence of iron deficiency is still 35% in a developed country like Belgium.
- 10% of pregnant women with iron deficiency will have thyroid autoimmunity and 20% will have subclinical hypothyroidism.
According to
WHO the prevalence of anemia in pregnancy is nearly 40% worldwide, with iron
deficiency being the major cause.[1]
A small
Belgian study published in European Journal of Endocrinology on July 22, 2016
linked low serum iron with increased risk of thyroid autoimmunity and hypothyroidism
in pregnancy.[2] It
was a nested cross sectional study as a part of ongoing data collection on
pregnant woman at a single tertiary center in Université Libre de Bruxelles in
Belgium.
The analysis
included 1900 study participants in the first trimester of pregnancy. Iron
deficiency was diagnosed when ferritin levels were < 15 μg/L, subclinical
hypothyroidism was defined as a TSH level > 2.5 mIU/L and thyroid peroxidase
antibodies(TPO-abs) was > 60 kIU/L defined thyroid autoimmunity(TAI).
Iron is
necessary for the normal functioning of thyroid peroxidase(TPO) which is a heme-containing enzyme catalyzing the two
initial steps in thyroid hormone synthesis.
Nearly one
third of the women suffered from iron deficiency, and in these women
significant association was found between low iron and thyroid autoimmunity
(10% versus 6%) and subclinical hypothyroidism (20% versus 16%) as compared to
women with normal iron levels.
The study
co-author Kris Poppe, MD, an endocrinologist opined that in his daily
practice, those women who are often
referred to him for thyroid dysfunction often seems to have low iron levels concurrently.
It is a very
small study which does not have significant impact on clinical practice, nor
does it proves causation. Low Ferritin levels might be due to other nutritional
deficiency or poor diet. But, it does emphasize on the need for replicating the
study in different population, with larger data.
Dr. Kris
Poppe also stressed the need for checking the iron levels in first trimester of
pregnancy or before planning the pregnancy so that any nutritional deficiency
could be corrected.
The
researchers are planning to design studies that look into impact of low iron
and thyroid dysfunction on pregnancy outcomes.
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