Impact of iodine deficiency on thyroid function in pregnant African women — A possible factor in the genesis of ‘small for dates’ babies |
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| Authors: | Santosh C Das Uche P Isichei Aminu Z Mohammed Abraham A Otokwula Abiodun Emokpae |
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| Institution: | (1) Department of Chemical Pathology, Aminu Kano Teaching Hospital, P.M.B. 3452, 700 001 Kano, Nigeria;(2) Department of Chemical Pathology, University of Jos, Jos, Nigeria;(3) Department of Pathology, Aminu Kano Teaching Hospital, P.M.B. 3452, 700 001 Kano, Nigeria |
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| Abstract: | The effect of iodine deficiency (ID) on thyroid function in African women during pregnancy and postnatal period was examined,
for which very limited information is available. Serum T4, T3, TSH, TBG, thyroxine binding capacity (TBK), free thyroxine index (FT4I=T4/TBK) and T4/TBG were determined by ELISA technique in 32 pregnant women (resident of Plateau state, Nigeria- an ID zone) through pregnancy
upto term delivery, and in 5 women up to 6 weeks post delivery. Urinary iodide level was measured at delivery to determine
the degree of iodine deficiency. Results were matched with a non pregnant control comprising 44 subjects. 5555 birth weights
(BW) of term babies in the region were analysed to determine the prevalence of ‘small for dates’ (SFD) babies in the population.
Results show that the level of serum FT4I was elevated very significantly at late gestation (P<.001) but the women were not hyperthyroid, suggesting a marked disturbance
in binding of T4 with TBG during pregnancy. Five women with SFD babies were found in ‘compensated hypothyroid state’ and showed a significant
depression (p<.01) in serum T4/TBG, T4, FT4I and T3 levels to a low normal range, with a concurrent significant rise (p.<.001) in TSH level (above normal range) throughout pregnancy.
Incidence of SFD babies was higher (p.<.001) in ID zone (Bassa 15.2%) compared to control zone (Jos 9.8%). It is concluded
that a state of maternal ‘subclinical (compensated) hypothyroidism’ during pregnancy possibly plays an important role in the
aetiopathogenesis of SFD babies in Africans. A normal reference range for thyroid parameters at various stages of pregnancy
in healthy African women is established for the first time. |
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| Keywords: | Africans Iodine deficiency Pregnancy Thyroid function |
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