A Young Woman With Palpitations and Abnormal Thyroid Test Results

Author:
Ronald N. Rubin, MD—Series Editor

Citation:
Rubin RN. A young woman with palpitations and abnormal thyroid test results. Consultant. 2017;57(11):655-656.

A 33-year-old woman presented with palpitations of several months’ duration. She reported having the sensation of a racing heartbeat very frequently on most days. The sensations occurred at rest and during activity. She had no sensation of skipped or irregular heartbeats, and she reported no other cardiac symptoms such as chest pain or dyspnea.

She was an otherwise healthy woman who is a schoolteacher and a mother of two. She was taking no chronic medications. She was thin, and she noted difficulty in putting on weight despite having an excellent appetite. She had noted frequently feeling warm coincident with her cardiac symptoms.

Physical examination revealed a healthy appearing, thin woman with a pulse rate of 108 beats/min and regular, a blood pressure of 105/65 mm Hg, and a normal temperature. Her neck was full with a palpable thyroid but without bruits. Cardiac examination revealed tachycardia with no murmurs or gallops. She had a fine, bilateral, symmetric tremor of the hands and fingers. She had mild eyelid retraction but normal extraocular muscle function and no orbital pain.

Results of initial laboratory tests included a normal blood glucose level and glycated hemoglobin level. Electrocardiography findings confirmed the presence of sinus tachycardia.

Her free thyroxine (FT₄) level was 6.0 ng/dL (reference range, 0.7-1.9 ng/dL), and her serum thyrotropin level was 0.2 mIU/L (reference range, 0.5-6.0 mIU/L).

Answer: D is the correct statement

This patient’s presentation is typical, even classic, for Graves disease, the most common cause of hyperthyroidism worldwide. The woman also displays the concordant finding of ophthalmopathy, mild in her case, which usually occurs within 1 year of the onset of a hyperthyroid state and is present in more than 50% of cases of Graves disease, depending on the extent of ocular evaluation.¹

Answers A and B relate to the diagnosis of Graves disease. Excellent and clinically useful algorithms exist for making the diagnosis.² The finding of an enlarged and overactive thyroid, an accelerated heart rate, and ocular abnormalities are the typical signs of Graves disease. Initial tests include measuring serum FT₄ and thyrotropin levels. A low thyrotropin level and a high FT₄ level confirm the presence of an overactive, autonomous thyroid and biochemical hyperthyroidism. Clinical findings of tachycardia, weight loss, and tremor demonstrate clinical hyperthyroidism in addition to biochemical hyperthyroidism. The goiter and other physical examination findings and the results of basic laboratory tests complete the picture of Graves disease, which was diagnostically adequate in our patient’s case.

A variety of further tests are often performed to more precisely define the clinical situation or to confirm the diagnosis in more subtle presentations. In patients without obvious diffuse goiter, a radioactive iodine 131 thyroid scan can confirm homogeneous increased uptake. Testing for the presence of thyrotropin-receptor antibodies (which are basic to the autoimmune pathophysiology of Graves disease) is 99% sensitive and specific for the detection of Graves disease but is not considered mandatory for typical cases such as that of the patient presented here,² so Answer A is not correct as stated. Similarly, orbital imaging can more precisely demonstrate the extent of orbital disease, but again it is not required in more routine cases, making Answer B incorrect, as well. An example of an indication for such imaging would be the finding of an asymmetric eye abnormality.^1,3

Answers C and D concern therapies for established cases of Graves disease. Each of the 3 treatment options—antithyroid medications, radioactive iodine ablation, and thyroidectomy—has advantages and disadvantages.

In the United States and Europe, the use of antithyroid medications to attempt a complete remission has evolved as the preferred first choice in most cases.^2,4 Thus, Answer D is correct here. This therapy is “easy”—outpatient, oral medications, inexpensive, and with a low incidence of adverse effects. A complete remission rate can be expected in approximately 50% of cases. The relapse rate is high, but there is no surgical risk or radiation exposure (our patient is a woman of childbearing age) and less-permanent residual hypothyroidism.

The other therapies are available should medication fail or relapse occur. Radioactive iodine is effective and relatively inexpensive. It should not be used in cases with active, significant ophthalmopathy, and it eventually will result in hypothyroidism requiring lifelong medication in most patients treated with it, perhaps making it a better choice in elderly patients. 

Surgery is by far the most expensive option. Although thyroidectomy is far safer than it had been in years past, it nevertheless is a serious surgical procedure, with complications including laryngeal nerve paralysis and hypoparathyroidism in 1% to 4% of cases.^2,4 It is rarely the initial choice, so Answer C is not correct.

Patient Follow-Up

The patient’s serum thyrotropin-receptor antibodies were measured at 4.2 IU/L (reference range, ≤ 1.75 IU/L), and the results of a radioactive iodine scan revealed homogeneous increased uptake, both of which more than confirmed the diagnosis of Graves disease. Oral β-blocker therapy with propranolol was initiated to help control her tachycardia and tremor. In view of her young age, the choice for initial therapy was antithyroid drugs, specifically methimazole, 20 mg/d, in an attempt to induce a clinical remission.

After 6 months of a planned 12-month course, she was biochemically euthyroid, without tachycardia or tremor, and no longer required β-blockers. The plan was to continue the antithyroid medication for at least a 12-month period of a sustained euthyroid state.

Ronald N. Rubin, MD, is a professor of medicine at the Lewis Katz School of Medicine at Temple University and is chief of clinical hematology in the Department of Medicine at Temple University Hospital in Philadelphia, Pennsylvania.

References:

1. Bartalena L, Tanda ML. Graves’ ophthalmopathy. N Engl J Med. 2009;​360(10):994-1001.
2. Smith TJ, Hegedüs L. Graves’ disease. N Engl J Med. 2016;375(16):1552-1563.
3. Bahn RS. Graves’ ophthalmopathy. N Engl J Med. 2010;362(8):726-738.
4. Burch HB, Cooper DS. Management of Graves’ disease: a review. JAMA. 2015;314(23):2544-2554.