Anxious Woman With Unexplained Weight Loss

A 42-year-old woman complains of anxiety, unexplained weight loss, and palpitationsthat started about 3 weeks earlier. She denies fever, trauma, and newstress. She has a history of several urinary tract infections for which imagingfailed to reveal any predisposing factors; all were successfully treated withmedication. The remainder of the history is unremarkable.

The patient is a nervous, mildly obese woman whose clothes appear to betoo large for her. Temperature is 37.2C (99F); heart rate, 103 beats perminute and normal rhythm; respiration rate, 24 breaths per minute; and bloodpressure, 148/96 mm Hg. Mild exophthalmos is evident, although the patientdenies any changes in visual acuity. The thyroid gland is smooth and diffuselyenlarged; no adenopathy is noted. Lungs are normal. Results of a neurologicexamination are also normal. The patient's thyroid-stimulating hormone (TSH)level is markedly low.

Which diagnostic test would you order next-and why?

WHICH TEST-AND WHY:

The patient's symptoms and low TSH level suggest athyrotoxic state. A nuclear medicine thyroid study can help distinguish betweenthe various kinds of thyrotoxic states:

• Homogeneous enlargement of the thyroid gland is mostconsistent with Graves' disease.
• An enlarged gland with a heterogeneous appearancesuggests a toxic multinodular goiter.
• A focal area of increased activity within the gland-withsuppression of activity in the remainder of the gland-ismost consistent with a toxic adenoma.

Identification of the type of thyrotoxic state has importanttherapeutic implications. A multinodular goiter ismore resistant to therapy than Graves' disease and thus istreated with higher doses of radioiodine (¹³¹I). A toxic adenomais treated with the maximum dose of ¹³¹I allowed inan outpatient setting. The reason for using the maximumdose is that the toxic portion of the gland receives most ofthe therapeutic effect, and the suppressed portion of thegland is left intact. As a result, treated patients often revertto a euthyroid state after therapy.

Figure 1

Results of the thyroid study. This patient's studyis performed with 10 mCi of technetium-99m pertechnetateand a low dose of ¹³¹I for uptake measurements.A marker image, obtained to assess gland size, revealsenlargement of the thyroid; the gland occupies morearea than expected between the chin and the sternalnotch (Figure 1). Three subsequent images-a highresolutionfrontal planar image, a right anterior obliqueimage, and a left anterior oblique image (Figure 2)-together with the results of palpation confirm that thegland is homogeneously enlarged. Iodine uptake iselevated at 48%.

Given the homogeneous enlargement of this patient'sthyroid gland and the elevated iodine uptake, Graves'disease is diagnosed.

After a negative result on a pregnancy test is obtained,β-blocker therapy is started to help reduce cardiacsymptoms. The patient is subsequently treatedwith 10 mCi of ¹³¹I.

Outcome of this case. At 6-month follow-up, the patient'sTSH level is still low but is rising. Her symptomshave dramatically subsided.