Thyroid Hormone Dose Change At Conception
"We suggest that women with hypothyroidism be instructed to increase their usual levothyroxine dose by two additional doses each week immediately upon confirmation of pregnancy and to contact their healthcare provider so that a program of test-guided doses can be instituted."
It is unusual for a medical study to direct women to change their medication dose and *then* call their doctor, such is the weight of evidence supporting this critical step to help you stay pregnant when the thyroid is already compromised. The researchers emphasize that:
"...it is clear that the requirement for thyroid hormone increases very early in pregnancy, typically before the first obstetrical visit."
Many thousands of babies (12,000-16,000) are born each year in the US to hypothyroid women due to the lack of thyroid testing in pregnancy which is thought to have an adverse effect on babies neurological development. This can cause various developmental, speech and hearing delays and low IQ in children and hypothyroidism in pregnancy is also associated with miscarriage, stillbirth, breech presentation, and premature birth, the study authors note that:
"Hypothyroidism during pregnancy has been associated with impaired cognitive development and increased fetal mortality"
This study from Brigham And Women's Hospital-Harvard Medical School discovered that 85% of women needed to increase their thyroid hormone dose in early pregnancy and the average dose increase needed was 47% by eight weeks of pregnancy. For some the increased demand for thyroid hormone was noticed as early as the fifth week of gestation.
During the early weeks of pregnancy - the first trimester - the fetus is wholly dependent upon the mother for thyroid hormone, specifically T4 which is critical for brain development and growth. The dose of thyroid hormone a woman is taking pre-conceptually is the dose that is correct for *their* bodies needs and extra is required to cater to the needs of a rapidly growing and developing baby. Lead researcher Erik K. Alexander stated that:
"Too little (thyroid hormone), and the baby risks impaired mental development and even death"
An editorial regarding the study from Anthony Toft, MD, of the Royal Infirmary in Edinburgh, Scotland, alternately suggests that women could simply increase their daily dose of thyroid hormone by 25 to 50 micrograms until their physician determines more exactly what is appropriate.
Some progressive physicians do test thyroid hormones upon confirmation of pregnancy and abide by these new recommendations. Others physicians may not test your thyroid in pregnancy at all - unless you ask - and even then, they may be reluctant to adjust your treatment because they are unfamiliar with the new guidelines. The authors clearly conclude that:
"Levothyroxine requirements increase as early as the fifth week of gestation. Given the importance of maternal euthyroidism for normal fetal cognitive development, we propose that women with hypothyroidism increase their levothyroxine dose by approximately 30 percent as soon as pregnancy is confirmed. Thereafter, serum thyrotropin levels should be monitored and the levothyroxine dose adjusted accordingly."
Women with healthy thyroids are able to speed up their own production of thyroid hormone assisted by the pregnancy hormone HCG - which also has a thyroid stimulating effect. Women with a history of poor thyroid health - even if very mild - are likely to have trouble meeting the needs of a rapidly developing baby and may need the extra level of care proposed by this study.
I hope that this information helps you to get good thyroid care when you conceive to protect your pregnancy and your baby from needless harm.
This article is intended for informational purposes only and is NOT intended to diagnose, offer medical or nutritional treatment or replace medical or nutritional advice for which you should consult a suitably qualified physician or dietitian.
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Timing and Magnitude of Increases in Levothyroxine Requirements during Pregnancy in Women with Hypothyroidism Erik K. Alexander, M.D., Ellen Marqusee, M.D., Jennifer Lawrence, M.D., Petr Jarolim, M.D., Ph.D., George A. Fischer, Ph.D., and P. Reed Larsen, M.D.
N Engl J Med 2004; 351:241-249 July 15, 2004
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