{"id":166,"date":"2016-06-10T15:16:17","date_gmt":"2016-06-10T20:16:17","guid":{"rendered":"http:\/\/obgynmorningrounds.com\/blog6\/?page_id=166"},"modified":"2020-09-07T12:11:43","modified_gmt":"2020-09-07T17:11:43","slug":"medical-problems-in-pregnancy-thyroid-disease","status":"publish","type":"page","link":"https:\/\/obgynmorningrounds.com\/blog6\/lectures\/obstetrics\/medical-problems-in-pregnancy-thyroid-disease\/","title":{"rendered":"Medical Problems in Pregnancy: Thyroid Disease"},"content":{"rendered":"<p><iframe loading=\"lazy\" src=\"https:\/\/player.vimeo.com\/video\/112396760\" width=\"640\" height=\"360\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p>[powerpress]<\/p>\n<input type='hidden' bg_collapse_expand='69ea1e05e46e23021219308' value='69ea1e05e46e23021219308'><input type='hidden' id='bg-show-more-text-69ea1e05e46e23021219308' value='Show Transcript'><input type='hidden' id='bg-show-less-text-69ea1e05e46e23021219308' value='Hide Transcript'><button id='bg-showmore-action-69ea1e05e46e23021219308' class='bg-showmore-plg-button bg-red-button  '   style=\" color:#fffcfc;\">Show Transcript<\/button><div id='bg-showmore-hidden-69ea1e05e46e23021219308' >\n<p class=\"p1\">A number of predictable changes occur in the thyroid gland during pregnancy that has consequences for those\u00a0evaluating and managing pregnant patients.<\/p>\n<p class=\"p1\">The thyroid gland normally enlarges as much as 18% in volume, a change that can be measured sonographically,\u00a0and occasionally detected clinically. A more significant change may reflect an underlying abnormality.<\/p>\n<p class=\"p1\">Inadequate amounts of iodine intake can lead to a maternal goiter. There is both increased renal clearance of\u00a0iodine and increased fetal uptake of iodine can lead to maternal goiter if maternal iodine intake does not\u00a0match these losses.<\/p>\n<p class=\"p1\">Thyroid nodules occur with the same frequency during pregnancy as in non-pregnancy, and are evaluated\u00a0with fine needle aspiration.\u00a0In the event a thyroid cancer is found, surgery is generally postponed, without penalty, until after delivery, to\u00a0reduce surgical complications.<\/p>\n<p class=\"p1\">Human chorionic gonadotropin, or HCG, has a mild, direct stimulatory effect on thyroid hormone production.<\/p>\n<p class=\"p1\">During the first trimester, as maternal HCG levels rise, maternal free T4 and T3 levels also rise. This elevation\u00a0usually remains at the upper limit of normal, but is accompanied by a reactive drop in TSH.<\/p>\n<p class=\"p1\">Whenever HCG levels are unusually elevated, for example with multiple gestations, hyperemesis gravidarum, or\u00a0gestational trophoblastic disease, these changes in thyroid indices can be even more dramatic. In such cases, the\u00a0patient may develop a transient and usually subclinical hyperthyroidism that occasionally causes some mild\u00a0symptoms.<\/p>\n<p class=\"p1\">Estrogen, produced in large quantities during pregnancy, leads to a significant increase in TBG because of\u00a0increased production and decreased clearance. This increased TBG binds more thyroxine and triiodothyronine.<\/p>\n<p class=\"p1\">Consequently, if a pregnant woman\u2019s total T4 or total T3 is measured, they often will both be elevated, reflecting\u00a0this increase in bound hormone. But even though the total T4 and T3 are elevated, the free, unbound T4 and T3\u00a0will be normal.<\/p>\n<p class=\"p1\">So, considering the HCG and estrogen changes, if a pregnant woman in her first trimester were to be evaluated\u00a0for thyroid hormone levels, it would not be surprising to find elevated total T4 and T3, and a modestly\u00a0depressed TSH. Someone who doesn\u2019t understand these normal pregnancy changes might be tempted to\u00a0conclude that this woman is hyperthyroid, but that person would likely be wrong. If they were to test her free T4\u00a0and T3, they would find normal values in this symptom-free patient.<\/p>\n<p class=\"p1\">That\u2019s not to say that hyperthyroidism does not exist in early pregnancy. To the contrary, uncontrolled or poorly\u00a0controlled hyperthyroidism is associated with a number of adverse pregnancy outcomes, including:<\/p>\n<ul>\n<li class=\"p1\">Spontaneous abortion<\/li>\n<li class=\"p1\">Stillbirth<\/li>\n<li class=\"p1\">Preterm labor<\/li>\n<li class=\"p1\">Low birth weight<\/li>\n<li class=\"p1\">Pre-eclampsia<\/li>\n<li class=\"p1\">Maternal heart failure<\/li>\n<\/ul>\n<p class=\"p1\">The most common cause of overt hyperthyroidism during pregnancy is Grave\u2019s disease, although there can\u00a0certainly be other causes.<\/p>\n<p class=\"p1\">Because of the normally elevated total T4 and T3, and the normal modest suppression of TSH during\u00a0pregnancy, the diagnosis of hyperthyroidism hinges on the elevation of Free T4 and T3, accompanied by a TSH\u00a0level &lt; 0.01 mU\/L.<\/p>\n<p class=\"p1\">Beta blockers, thionamides, and surgery can be used to treat hyperthyroidism during pregnancy, but there are\u00a0complexities regarding the optimum gestational age and duration of use. Radioactive iodine therapy is not used\u00a0during pregnancy as it crosses the placenta and concentrates in the fetal thyroid gland.<\/p>\n<p class=\"p1\">Pregnancies complicated by hyperthyroidism require close monitoring of the fetus for evidence of\u00a0thyrotoxicosis, cardiac and growth problems. Thyroid hormone does cross the placenta, but only to a limited\u00a0extent. Same with TSH. But TSH-receptor antibodies do cross the placenta in clinically significant amounts and\u00a0can lead to fetal hyperthyroidism, with tachycardia, cardiac failure, fetal hydrops, fetal goiter and poor growth.<\/p>\n<p class=\"p1\">Hypothyroidism may also complicate pregnancy and also carries significant risks, among them:<\/p>\n<ul>\n<li class=\"p1\">Preterm delivery<\/li>\n<li class=\"p1\">Pre-eclampsia<\/li>\n<li class=\"p1\">Perinatal morbidity and mortality<\/li>\n<li class=\"p1\">Cognitive impairment<\/li>\n<li class=\"p1\">Placental abruption<\/li>\n<\/ul>\n<p>But there are two mitigating factors to the problem of hypothyroidism during\u00a0pregnancy. The more severe forms of hypothyroidism are the ones more often\u00a0associated with these adverse outcomes, but those are also the women least likely to\u00a0get to the point in pregnancy where these issues can arise, because of anovulation\u00a0and infertility, and also the increased miscarriage rates found among these patients\u00a0with the more severe forms of the disease.<\/p>\n<p class=\"p1\">Because of the normal lowering of TSH during pregnancy, the diagnosis of\u00a0hypothyroidism is based on a TSH &gt; 2.5, at least during the first trimester. Screening\u00a0for this condition is controversial, with some physicians recommending universal\u00a0screening in the first trimester, and others recommending testing only of those\u00a0symptomatic or at high risk.<\/p>\n<p class=\"p1\">Treatment involves aggressive use of thyroid hormone, sufficient to make the patient\u00a0euthyroid, with TSH levels less than 2.5 and greater then 0.1. Because it may take weeks for full equilibration to\u00a0occur, followup TSH levels are monitored 4 weeks after any change in dosage, and many physicians will follow\u00a0TSH at 4 week intervals throughout the pregnancy.<\/p>\n<p class=\"p1\">For women with pre-existing hypothyroidism who are already on a stable dose of thyroid hormone, their dosage\u00a0needs can be expected to increase up to 50% during pregnancy. Because it is important to avoid low thyroid\u00a0levels at any time during pregnancy, many physicians will increase the pre-pregnancy thyroid hormone dose by\u00a030% at the first prenatal visit, and then follow the 4-week TSH levels, making additional adjustments as needed\u00a0to keep the TSH between 0.1 and 2.5.<\/p>\n<p class=\"p1\">Postpartum, up to 10% of women will experience a transient thyroiditis, and up to 25% among those with type 1\u00a0diabetes. During the hyperthyroid phase, beta blockers may be needed to control symptoms. During the\u00a0hypothyroid phase, thyroxine may be needed, and is usually continued for 6 months before tapering to\u00a0determine if the hypothyroid status will be permanent, or has resolved.<\/p>\n<p>   <\/div><br \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>[powerpress]<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":79,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-166","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/pages\/166","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/comments?post=166"}],"version-history":[{"count":4,"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/pages\/166\/revisions"}],"predecessor-version":[{"id":916,"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/pages\/166\/revisions\/916"}],"up":[{"embeddable":true,"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/pages\/79"}],"wp:attachment":[{"href":"https:\/\/obgynmorningrounds.com\/blog6\/wp-json\/wp\/v2\/media?parent=166"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}