A 30-year-old woman comes to the office due to tiredness for the past 3 months. She has been unable to exercise due to excessive fatigue and muscle cramps. The patient has had no cold intolerance, constipation, or dry skin. She states, "My menstrual cycles have been unpredictable and very heavy." Medical history is notable for episodic migraines, for which she began taking topiramate 6 months ago. The patient initially had significant weight loss after starting topiramate, but she has regained most of the weight over the last 2 months and continues to have occasional migraines. She also has a history of chronic anxiety and an episode of nephrolithiasis a few months ago. The patient lives alone, is not sexually active, and has had no pregnancies. She does not use tobacco, alcohol, or illicit drugs. The patient's sister underwent a thyroidectomy for unknown reasons. Blood pressure is 136/80 mm Hg and pulse is 68/min. BMI is 28 kg/m². The thyroid gland is normal in size and nontender. Deep tendon reflexes are normal; the remainder of the examination is unremarkable. Serum TSH is 5.7 µU/mL. Repeat TSH a month later is 5.6 µU/mL, and free T4 is normal.
Which of the following is the best next step in management of this patient?

Question

Quizplus · Accepted Answer

Explanation: 11ec2b69_c13c_f2b0_8f63_b7e3abb213b8_MD0005_00 Subclinical hypothyroidism (SCH) is defined as an elevated serum TSH level with a normal free thyroxine. The most common cause is chronic lymphocytic (Hashimoto) thyroiditis. The decision to treat SCH with levothyroxine depends on the magnitude of TSH elevation, age, presence of goiter, and whether there are symptoms definitely attributable to hypothyroidism. In addition, high circulating levels of anti-thyroid peroxidase (anti-TPO) antibodies (seen in >90% of patients with Hashimoto thyroiditis) are associated with progression to overt hypothyroidism and can identify patients who are likely to benefit from treatment. This patient has a mild TSH elevation and nonspecific symptoms (eg, fatigue, weight loss followed by weight gain), some of which could be attributable to medications (eg, topiramate). Measuring the level of anti-TPO antibodies would help establish the diagnosis of Hashimoto thyroiditis and facilitate management decisions. (Choices B, C, and E) Thyroid ultrasound is primarily indicated for evaluation of thyroid nodules. Fine-needle aspiration biopsy is indicated to evaluate nodules with suspicious findings on ultrasound and to rule out malignancy in patients with a rapidly enlarging goiter. Large-bore needle biopsy has been largely replaced by fine-needle aspiration biopsy but is occasionally used when a larger amount of tissue is needed for evaluation. This patient has no goiter or nodules; ultrasound and biopsy are not indicated. (Choice D) Radionuclide thyroid scan is primarily used in the evaluation of hyperthyroidism and can distinguish between Graves disease (diffuse uptake) and nodular disease (focal uptake). Uptake in Hashimoto thyroiditis is often heterogeneous but is nonspecific and has little utility for diagnosis. Educational objective: Subclinical hypothyroidism is an elevated serum TSH level with a normal free thyroxine. Treatment is warranted for most patients with significant elevations in TSH, goiter, or convincing hypothyroid symptoms. For asymptomatic patients with mild elevations in TSH, an elevated antithyroid peroxidase antibody titer increases the likelihood of progression to overt hypothyroidism and can identify patients who are likely to benefit from treatment. References: Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. (http://www.ncbi.nlm.nih.gov/pubmed/22954017) Subclinical hypothyroidism: Should we treat? (http://www.ncbi.nlm.nih.gov/pubmed/28406057)

A 30-Year-Old Woman Comes to the Office Due to Tiredness