5 Cases to Hone Your Diagnostic Skills
Weight Loss and Anxiety in a Young Woman
1. A 32-year-old woman presents with weight loss of 6.4 kg (14 lb) during the past 8 months and diarrhea of recent onset. Menstruation had ceased 10 weeks earlier. She appears anxious, with pressured speech. Physical examination detects baseline sinus tachycardia, sweaty palms, and a diffusely enlarged thyroid gland. Laboratory tests reveal a thyroid-stimulating hormone (TSH) level of 0.00 μU/mL (normal, 0.45 to 4.5 μU/mL), a free thyroxine (FT4) level of 4.8 ng/dL (normal, 0.61 to 1.76 ng/dL), and a positive thyroid-stimulating immunoglobulin (TSI) level with high titer.
This is a classic presentation of hyperthyroidism caused by Graves’ disease. The diagnosis can be made based on clinical presentation, physical examination, and selected laboratory tests. Further evaluation with a radioactive iodine (RAI) uptake and thyroid scan would reveal an enlarged gland with increased uptake and confirm the diagnosis. The tests would also yield necessary dosing information if the patient were to be treated with RAI ablation. Alternatively, she could be treated with antithyroid medications or surgery. Subsequent to surgery, thyroid hormone replacement therapy with levothyroxine would be needed. If this patient were pregnant, treatment options would change. RAI ablation would now be contraindicated, and the patient could be offered antithyroid treatment with propylthiouracil (PTU). Following pregnancy, RAI ablation with subsequent thyroid replacement therapy would be recommended.
An Elderly Man With Recent Atrial Fibrillation
2. A 76-year-old man with known heart disease is admitted to the hospital because of new onset of shortness of breath, fatigue, and atrial fibrillation. He denies weight loss, nervousness, and insomnia. There is no evidence of an acute myocardial infarction or pulmonary embolus. On physical examination, his heart rate is 136 beats per minute; beats are irregularly irregular; and fine rales are heard at both lung bases. His blood pressure is 152/82 mm Hg, without orthostatic changes. Results of laboratory tests indicate a hemoglobin level of 14.6 g/dL, a TSH level of 0.02 μU/mL (normal, 0.45 to 4.5 μU/mL), and an FT4 level of 3.3 ng/dL (normal, 0.61 to 1.76 ng/dL).
An elderly patient with hyperthyroidism secondary to Graves’ disease, toxic multinodular goiter, or toxic adenoma often presents without classic symptoms. A diagnosis of Graves’ disease is confirmed by measurement of TSI and an RAI uptake and thyroid scan. Imminent treatment includes βblockers (and corticosteroids, if necessary) to control the hyperthyroid state, which is now causing secondary atrial fibrillation and congestive heart failure. βBlockers will control the tachycardia and reduce the risk of heart failure; corticosteroids will block the peripheral conversion of T4 to triiodothyronine (T3). PTU might be useful for inhibiting intrathyroidal hormone production (oxidation and organification) and the peripheral conversion of T4 to the metabolically active T3. Plans should be made for RAI ablation, followed by thyroid hormone replacement therapy. In cases such as this, the atrial fibrillation is usually not converted to a normal sinus rhythm until the hyperthyroid state is successfully treated. Anticoagulation therapy should be considered as well.
Nodule in a Woman With Insomnia
3. A 29-year-old woman presents for her yearly pelvic examination and Pap smear. She complains of insomnia and nervousness. Physical examination reveals an enlargement of the left lobe of the thyroid gland, which suggests the presence of a nodule. Laboratory test results reveal a TSH level of 0.02 μU/mL (normal, 0.45 to 4.5 μU/mL) and an FT4 level of 2.3 ng/dL (normal, 0.61 to 1.76 ng/dL).
To confirm a diagnosis of hyperthyroidism secondary to toxic adenoma. in a patient with abnormal levels of TSH and FT4, fine-needle aspiration and biopsy (FNAB) of the nodule are indicated. An RAI uptake and thyroid scan can be used to investigate the possibility of “other” adenomas and to help determine the dosage of 131I for subsequent radioiodine therapy. Many physicians turn to ultrasonography, but the initial evaluation that consists of TSH and FT4 measurement and FNAB is sufficient for diagnosis. Ultrasonography cannot distinguish benign from malignant tissue.
Treatment is either surgery (partial thyroidectomy) or RAI ablation. If the nodule persists following treatment with RAI ablation, a second tissue biopsy is indicated.
Woman With Tremors Following Weight Loss
4. A 28-year-old hospital nurse presents for evaluation of palpitations and tremors that occur with writing. She has intentionally lost 10 kg (22 lb) during the past 4 months. She requests a sleeping pill and some lorazepam to relieve her “shakes.” She is nervous and fidgets during the examination, and her reflexes demonstrate 2-beat clonus. Laboratory tests reveal a TSH level of 0.01 μU/mL (normal, 0.45 to 4.5 μU/mL)and an FT4 level of 3.9 ng/dL (normal, 0.61 to 1.76 ng/dL). You suspect hyperthyroidism and order an RAI uptake and thyroid scan. Surprisingly, results of the tests reveal “decreased uptake of 123I and a normal-sized gland, with no hot or cold areas identified.”
Factitious hyperthyroidism should be suspected—and confirmed with additional history taking. No doubt this woman has been taking exogenous thyroid hormone to facilitate weight loss. This syndrome is often found in hospital and medical workers who are aware of this hormone’s metabolic effect and have access to samples. Factitious hyperthyroidism is distinguished from iatrogenic hyperthyroidism by the fact that the latter occurs in patients for whom more than the recommended dose for the treatment of hypothyroidism is prescribed. Another cause of decreased RAI uptake is subacute thyroiditis. A suppressed serum thyroglobulin level is consistent with factitious hyperthyroidism; this level is elevated in subacute thyroiditis.
Nervous New Mother
5. A 28-year-old woman presents with complaints of nervousness, trouble sleeping, and weight loss. She is 8 weeks postpartum and wants to return soon to her job as a coronary care unit nurse. Laboratory tests reveal a TSH level of 0.03 μU/mL (normal, 0.45 to 4.5 μU/mL) and an FT4 level of 3.4 ng/dL (normal, 0.61 to 1.76 ng/dL). Results of a test for TSI are negative.
Postpartum thyroiditis is a self-limited disease (lasting 6 to 9 months) that transiently evolves first through a state of hyperthyroidism, then hypothyroidism, before the patient returns to a euthyroid state.1 Depending on the time of testing and the clinical presentation, a presumptive diagnosis of hyperthyroidism or hypothyroidism may be made. Thyroid 123I uptake measurement is necessary to confirm the diagnosis. Because most patients return to a euthyroid state, no specific treatment is recommended, although hypothyroidism may persist in 20% to 25% of patients for 4 years.,2,3 Serial TSH measurements, explanation of the problem to the patient, and reassurance are indicated. The transient symptoms of hyperthyroidism may be managed with β-blockers.