A 32-year-old woman, gravida 3 para 2, comes to the office at 10 weeks gestation to establish prenatal care. She has mild nausea and anxiety and has not gained any weight during the pregnancy because of decreased food intake due to the nausea. The patient's first pregnancy was complicated by hyperemesis gravidarum but her second pregnancy was uneventful. She has no medical problems and her only medication is a daily prenatal vitamin. Her mother has a thyroid nodule and her father has type 2 diabetes mellitus, hyperlipidemia, and hypertension. The patient eats a vegan diet and does not use tobacco, alcohol, or illicit drugs. Blood pressure is 126/82 mm Hg and pulse is 94/min and regular. The thyroid gland is normal. There is no lid lag or proptosis. Chest auscultation is unremarkable. Laboratory results are as follows: Which of the following is the best next step in management of this patient?

Question

A 32-year-old woman, gravida 3 para 2, comes to the office at 10 weeks gestation to establish prenatal care.  She has mild nausea and anxiety and has not gained any weight during the pregnancy because of decreased food intake due to the nausea.  The patient's first pregnancy was complicated by hyperemesis gravidarum but her second pregnancy was uneventful.  She has no medical problems and her only medication is a daily prenatal vitamin.  Her mother has a thyroid nodule and her father has type 2 diabetes mellitus, hyperlipidemia, and hypertension.  The patient eats a vegan diet and does not use tobacco, alcohol, or illicit drugs.  Blood pressure is 126/82 mm Hg and pulse is 94/min and regular.  The thyroid gland is normal.  There is no lid lag or proptosis.  Chest auscultation is unremarkable.  Laboratory results are as follows:  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bec8_975c_8f63_e32880fdb3db_MD0005_00 Thyroid hormone production increases during pregnancy to cope with metabolic demands. This is accomplished by 2 mechanisms: Estrogen stimulates synthesis of thyroxine-binding globulin, leading to an increased pool of bound thyroid hormone. Thyroid hormone production subsequently increases to maintain free hormone levels. hCG (which shares a common alpha subunit with TSH and a very similar beta subunit) directly stimulates TSH receptors. This results in increased thyroid hormone production with feedback suppression of pituitary TSH release. In patients with normal thyroid function, the net effect can resemble subclinical hyperthyroidism with increased total T4, normal (or mildly elevated) free T4, and suppressed TSH. This patient is clinically euthyroid, with a physiologic increase in total T4 and decrease in TSH. Although she has nonspecific symptoms (eg, nausea, anxiety), her vital signs and thyroid examination are normal, with no evidence of lid lag (seen in most cases of hyperthyroidism) or proptosis (seen with Graves disease). No additional workup is necessary at this time. (Choice A) Free T4 assays in pregnancy are unreliably low due to assay artifact. Measurement of total T4 is preferred during pregnancy. (Choice B) Total T3 is primarily used as a secondary test for hyperthyroidism in patients with suppressed TSH and normal T4. This patient is clinically euthyroid and a T3 assay is not needed. (Choice D) Antithyroid drugs are used in pregnancy for the treatment of overt hyperthyroidism; propylthiouracil is preferred during the first trimester and methimazole in the second and third. This patient is clinically euthyroid; therefore, antithyroid treatment is not indicated. (Choice E) Thyroid ultrasound is indicated for the evaluation of thyroid nodules and multinodular goiter. This patient has a normal thyroid examination. Educational objective: Thyroid hormone production increases during pregnancy to cope with metabolic demands. Estrogen causes an increase in thyroxine-binding globulin, leading to increased total (but not free) thyroid hormone levels. hCG directly stimulates TSH receptors, causing increased production of thyroid hormones. References: Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society clinical practice guideline. (http://www.ncbi.nlm.nih.gov/pubmed/22869843)

A 32-Year-Old Woman, Gravida 3 Para 2, Comes to the Office