from Section 4 - Metabolic disorders
Published online by Cambridge University Press: 19 October 2009
Introduction
Endocrinopathies can complicate pregnancy with adverse maternal and fetal effects. Pregnancy can mask or mimic signs and symptoms of endocrine disease making diagnosis difficult.
Thyroid disease
Hyperthyroidism
Hyperthyroidism is relatively common in the general population and occurs in 2 of 1000 pregnancies. Graves disease causes 80–95% of cases of hyperthyroidism in pregnancy. Other causes include thyroiditis, toxic adenoma, multinodular goiter, viral thyroiditis, and tumors of the pituitary or ovary. Human chorionic gonadotropin (hCG), which peaks between 8 and 14 weeks, weakly stimulates thyroid stimulating hormone (TSH) receptors, and in some cases leads to transient hyperthyroidism associated with hyperemesis gravidarum. High levels of hCG with clinical hyperthyroidism may also be seen with gestational trophoblastic disease and multiple pregnancies.
Subclinical hyperthyroidism occurs in pregnancy (1.7% of all screened women), and, in the general population, has long-term sequelae such as osteoporosis, cardiovascular morbidity, and progression to overt thyrotoxicosis. These women have suppressed TSH but normal free thyroxine (T4) levels. African-American and parous women are more likely to be affected, but there are no adverse pregnancy outcomes. Identification of subclinical hyperthyroidism and treatment during pregnancy is unwarranted.
Thyrotoxic crisis (thyroid storm)
Thyroid storm is the most serious complication of hyperthyroidism. This exaggerated hypermetabolic state occurs in 2% of pregnancies complicated by hyperthyroidism with a reported maternal mortality rate of 15% and a 24% rate of stillbirth. Thyroid storm is often precipitated in women with Graves thyrotoxicosis by common obstetric complications such as hemorrhage, severe preeclampsia, and sepsis.
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