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Sub-clinical hypothyroidism and obstetric Outcomes


There is increasing awareness of the importance of maternal thyroid hormone for the development of the fetal brain early in pregnancy. Recent studies have suggested that a proportion of pregnant women are affected by thyroid inadequacy resulting in period s of decreased thyroid hormone production during pregnancy, with no apparent symptoms. We wish to clarify whether adverse maternal and fetal outcomes are significantly increased in women with such thyroid inadequacy, termed "sub-clinical hypothyroidism", and to quantify such effects, if present. This will have tremendous societal implications, not just with regard to the cost of long term care of impaired children, but also in terms of the vast opportunity cost to society from failure of those affected to achieve their potential.

A range of thyroid hormones will be studied at each term during pregnancy and after delivery. The first objective of this study is to establish normal ranges for these hormones at each time-point during pregnancy. At this time there is no uniform agreement on the appropriate cut-offs in hormone levels in order to make a diagnosis of sub-clinical hypothyroidism, or the severity of hypothyroidism that would require treatment. The literature suggests that our current laboratory techniques for testing thyroid hormones may be inadequate.

Our study will therefore employ highly sensitive laboratory techniques for quantifying these hormone levels. Preliminary work suggests that "mass spectrometry" technology is more accurate in the detection of thyroid hormones. In the event that mass spectrometry technology identifies that currently employed standard techniques for quantifying thyroid hormones result in an under diagnosis of sub-clinical hypothyroidism, the importance of this proposal will be to prompt timely intervention for such pregnancies, which should ultimately result in fewer children with sub-optimal neurological development.

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