A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 23-year-old primigravida presents to her physician’s office at 12 weeks gestation complaining of increased sweating and palpitations for the last week. She does not have edema or dyspnea, and had no pre-existing illnesses. The patient says that the symptoms started a few days after several episodes of vomiting. She managed the vomiting at home and yesterday the vomiting stopped, but the symptoms she presents with are persistent. The pre-pregnancy weight was 54 kg (119 lb). The current weight is 55 kg (121 lb). The vital signs are as follows: blood pressure 130/85 mm Hg, heart rate 113/min, respiratory rate 15/min, and temperature 37.0℃ (98.6℉). The physical examination is significant for diaphoresis, an irregular heartbeat, and a fine resting tremor of the hands. The neck is not enlarged and the thyroid gland is not palpable. The ECG shows sinus tachyarrhythmia. The thyroid panel is as follows:
Thyroid stimulating hormone (TSH) < 0.1 mU/L
Total T4 178 nmol/L
Free T4 31 pmol/L
Which of the following is indicated?
-
A
Ensure proper hydration and prescribe a beta-blockerCorrect. Gestational transient thyrotoxicosis (hCG-mediated) is self-limited and managed with hydration and beta-blockade only.
-
B
Manage with propylthiouracilIncorrect. PTU is reserved for true Graves disease in pregnancy (first trimester); not indicated for transient hCG-mediated thyrotoxicosis.
-
C
Prescribe methimazoleIncorrect. Methimazole is contraindicated in the first trimester (aplasia cutis, choanal/esophageal atresia); also not needed for transient hCG effect.
-
D
Recommend iodine radioablationIncorrect. Radioiodine ablation is ABSOLUTELY CONTRAINDICATED in pregnancy—destroys fetal thyroid.
-
E
Begin treatment with levothyroxineIncorrect. Levothyroxine is replacement therapy for HYPOthyroidism; administering it to a thyrotoxic patient with hCG-mediated transient hyperthyroidism would worsen her condition.
↑ Tap an answer to reveal the reasoning
Answer: A. A pregnant patient at 12 weeks with hyperthyroidism (low TSH, high T4) after recent hyperemesis is most likely experiencing GESTATIONAL TRANSIENT THYROTOXICOSIS due to hCG-stimulated thyroid activity, NOT Graves disease. Clues that distinguish it from Graves: nonpalpable, non-enlarged thyroid; no orbitopathy; symptoms followed a brief period of vomiting (hyperemesis gravidarum is the most extreme form of this hCG effect). hCG shares an alpha subunit with TSH and weakly stimulates the TSH receptor; in the first trimester, when hCG peaks, mild transient hyperthyroidism can occur. It is self-limited and resolves by ~14-18 weeks as hCG falls.
Management is SUPPORTIVE: hydration and a beta-blocker (propranolol, atenolol, or labetalol) for symptomatic tachycardia/tremor. Thionamides (PTU in the first trimester, methimazole after) are reserved for true Graves disease and are NOT indicated here because the condition is transient and self-limited. Radioiodine is ABSOLUTELY CONTRAINDICATED in pregnancy (destroys fetal thyroid).
Key teaching point: in Graves disease during pregnancy, PTU is preferred in the first trimester (methimazole has been associated with aplasia cutis and choanal/esophageal atresia), then switch to methimazole after 16 weeks because PTU carries a higher hepatotoxicity risk.
**Why each option:**
**A.** Correct. Gestational transient thyrotoxicosis (hCG-mediated) is self-limited and managed with hydration and beta-blockade only.
**B.** PTU is reserved for true Graves disease in pregnancy (first trimester); not indicated for transient hCG-mediated thyrotoxicosis.
**C.** Methimazole is contraindicated in the first trimester (aplasia cutis, choanal/esophageal atresia); also not needed for transient hCG effect.
**D.** Radioiodine ablation is ABSOLUTELY CONTRAINDICATED in pregnancy—destroys fetal thyroid.