New Guidelines Issued for Thyroid Disorders in Pregnancy

Insufficient thyroid activity during pregnancy is harmful to maternal and fetal health as well as to the child’s future intellectual development, according to emerging data that led to new guidelines released by the American Thyroid Association (ATA).¹ These guidelines highlight the role of thyroid function tests, hypothyroidism, thyrotoxicosis, iodine, thyroid antibodies and miscarriage or preterm delivery, thyroid nodules and cancer, postpartum thyroiditis, screening recommendations during pregnancy, and areas for future research.

The production of thyroid hormones and the body’s iodine requirements each increase by about 50% during pregnancy. Subsequently, the thyroid gland can enlarge by 10% in countries where iodine sources are sufficient and up to 20% to 40% in countries where there is iodine deficiency.¹ According to the members of the ATA Taskforce, “Pregnancy has a profound impact on the thyroid gland and thyroid function. . . . In essence, pregnancy is a stress test for the thyroid, resulting in hypothyroidism in women with limited thyroidal reserve or iodine deficiency.”¹

Subclinical thyroid disease and overt hypothyroidism and hyperthyroidism in pregnant women can have harmful effects. An extreme form of neurological damage caused by neonatal hypothyroidism that goes untreated is cretinism, which is characterized by gross mental retardation along with varying degrees of short stature, deaf mutism, and spasticity. There is also some evidence of an association between miscarriage and preterm delivery in women with normal thyroid function who test positive for thyroid peroxidase (TPO) antibodies; the strength of this association is being further studied.

The ATA issued 76 specific recommendations that cover the diagnosis and management of thyroid disease during pregnancy and the postpartum period. Examples of these guidelines include the following:

• Women with overt hypothyroidism or with subclinical hypothyroidism who test positive for TPO antibodies should be treated with oral levothyroxine.
• Use of other thyroid preparations, such as triiodothyronine or desiccated thyroid, to treat maternal hypothyroidism is strongly discouraged.
• Women with subclinical hypothyroidism in pregnancy who are not initially treated should be monitored for progression to overt hypothyroidism with serum thyroid-stimulating hormone and free thyroxine measurements every 4 weeks until 16 to 20 weeks gestation and at least once between 26 and 32 weeks gestation.

More Information

National Endocrine and Metabolic Diseases Information Service: Pregnancy and Thyroid DiseaseAutoimmune Thyroid Disease and Pregnancy 

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References:

Reference
1. Stagnaro-Green A, Abalovich M, Alexander E, et al, for the American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011;21(10). Epub ahead of print.