Case In Point: Hyperthyroidism: 5 Cases to Hone Your Diagnostic Skills

Weight Loss and Anxiety in a Young Woman1. A 32-year-old woman presents with weight loss of 6.4 kg (14 lb) during the past 8 months and diarrhea of recentonset. Menstruation had ceased 10 weeks earlier. She appears anxious, with pressured speech. Physical examination detectsbaseline sinus tachycardia, sweaty palms, and a diffusely enlarged thyroid gland. Laboratory tests reveal a thyroid-stimulatinghormone (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 basedon 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 replacementtherapy with levothyroxine would be needed.If this patient were pregnant, treatment options would change. RAI ablation would now be contraindicated, andthe patient could be offered antithyroid treatment with propylthiouracil (PTU). Following pregnancy, RAI ablationwith subsequent thyroid replacement therapy would be recommended.

An Elderly Man With Recent Atrial Fibrillation2.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 myocardialinfarction or pulmonary embolus. On physical examination, his heart rate is 136 beats per minute; beats are irregularlyirregular; and fine rales are heard at both lung bases. His blood pressure is 152/82 mm Hg, without orthostaticchanges. Results of laboratory tests indicate a hemoglobin level of 14.6 g/dL, a TSH level of 0.02 μU/mL (normal, 0.45to 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 adenomaoften presents without classic symptoms. A diagnosis of Graves' disease is confirmed by measurement of TSIand an RAI uptake and thyroid scan. Imminent treatment includes βblockers (and corticosteroids, if necessary) tocontrol 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 peripheralconversion of T₄ to triiodothyronine (T₃). PTU might be useful for inhibiting intrathyroidal hormone production (oxidationand organification) and the peripheral conversion of T₄ to the metabolically active T₃. Plans should be madefor RAI ablation, followed by thyroid hormone replacement therapy. In cases such as this, the atrial fibrillation isusually not converted to a normal sinus rhythm until the hyperthyroid state is successfully treated. Anticoagulationtherapy should be considered as well.

Nodule in a Woman With Insomnia3.A 29-year-old woman presents for her yearly pelvic examination and Pap smear. She complains of insomnia andnervousness. Physical examination reveals an enlargement of the left lobe of the thyroid gland, which suggests the presenceof 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 of2.3 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 TSHand FT₄, fine-needle aspiration and biopsy (FNAB) of the nodule are indicated. An RAI uptake and thyroid scan canbe used to investigate the possibility of "other" adenomas and to help determine the dosage of ¹³¹I for subsequent radioiodinetherapy. Many physicians turn to ultrasonography, but the initial evaluation that consists of TSH and FT₄measurement and FNAB is sufficient for diagnosis. Ultrasonography cannot distinguish benign from malignanttissue.

Treatment is either surgery (partial thyroidectomy) or RAI ablation. If the nodule persists following treatmentwith RAI ablation, a second tissue biopsy is indicated.

Woman With Tremors Following Weight Loss4. A 28-year-old hospital nurse presents for evaluation of palpitations and tremors that occur with writing. She hasintentionally lost 10 kg (22 lb) during the past 4 months. She requests a sleeping pill and some lorazepam to relieveher "shakes." She is nervous and fidgets during the examination, and her reflexes demonstrate 2-beat clonus. Laboratorytests 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 to1.76 ng/dL). You suspect hyperthyroidism and order an RAI uptake and thyroid scan. Surprisingly, results of the testsreveal "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 thiswoman has been taking exogenous thyroid hormone to facilitate weight loss. This syndrome is often found in hospitaland medical workers who are aware of this hormone's metabolic effect and have access to samples. Factitious hyperthyroidismis distinguished from iatrogenic hyperthyroidism by the fact that the latter occurs in patients for whommore 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 consistentwith factitious hyperthyroidism; this level is elevated in subacute thyroiditis.

Nervous New Mother5. A 28-year-old woman presents with complaints of nervousness, trouble sleeping, and weight loss. She is 8 weekspostpartum and wants to return soon to her job as a coronary care unit nurse. Laboratory tests reveal a TSH level of0.03 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 atest for TSI are negative.

Postpartum thyroiditis is a self-limited disease (lasting 6 to 9 months) that transiently evolves first through astate of hyperthyroidism, then hypothyroidism, before the patient returns to a euthyroid state.¹ Depending on thetime of testing and the clinical presentation, a presumptive diagnosis of hyperthyroidism or hypothyroidism may bemade. Thyroid ¹²³I uptake measurement is necessary to confirm the diagnosis. Because most patients return to aeuthyroid state, no specific treatment is recommended, although hypothyroidism may persist in 20% to 25% of patientsfor 4 years.,^2,3 Serial TSH measurements, explanation of the problem to the patient, and reassurance are indicated. Thetransient symptoms of hyperthyroidism may be managed with β-blockers.