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Old 10-20-2011
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A previously healthy 32-year-old woman from a small rural town comes to your office complaining of extreme anxiety and palpitations on several occasions during the past week. She denies having had episodes like these before, and she also notes feelings of excessive warmth. Her past history is remarkable only for a normal pregnancy six years ago, and she takes no medications. Her pulse is 110/min and blood pressure is 145/80 mm Hg. Her skin is moist, and she has a rim of sclera visible above the iris when looking straight ahead. She has a non-palpable thyroid and a 2/6 early systolic murmur on cardiac examination. There is a fine tremor in her hands and she has brisk, hyperactive reflexes bilaterally. Serum thyroid-stimulating hormone is 0.2 mcU/mL. Her child, who has also been subsequently healthy, accompanies his mother to the clinic today. During the visit, you notice that the child is extremely active and on examination is himself tremulous with a wide-eyed stare. As the town's family physician, you have seen several similar cases within the past month. Which of the following is the most likely explanation for these findings?


Accidental ingestion of thyroid hormone


Infectious thyroiditis


Over-supplementation with dietary iodine


Panic attacks


Self-administration of thyroid hormone
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Old 10-20-2011
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B. Infectious thyroiditis??
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Old 10-20-2011
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The correct answer is A. This patient and her son are clearly suffering from thyrotoxicosis, as evidenced by the findings on physical examination and blood tests. Their symptoms are the result of ingestion of thyroid hormone-containing ground beef. Two community outbreaks of thyrotoxicosis have been reported to result from the accidental ingestion of thyroid tissue from cattle. The tissue was removed along with neck muscle and ground up to prepare hamburger. These outbreaks were labeled "hamburger hyperthyroidism". Affected patients consumed large amounts of thyroid-hormone-containing ground beef and subsequently became hyperthyroid until their pantry stocks were depleted. Several weeks thereafter, they became hypothyroid because of the slow recovery time of the suppressed thyroid.
Infectious thyroiditis (choice B) would seem possible on the basis of this community "outbreak" and a similar syndrome among family members. However, no virus or bacterium has yet been described which infects only the thyroid gland in multiple different patients. Subacute (De Quervain’s) thyroiditis presents in a manner similar to the case above, except that it usually follows an upper respiratory illness. Viral infection and destruction of thyroid follicles result in the release of pre-formed thyroid hormone into the blood, causing thyrotoxicosis. Once the infection has resolved, hypothyroidism ensues for a brief period while the gland recovers.
Over-supplementation with dietary iodine (choice C) is possible iatrogenically following the administration of iodinated contrast media and amiodarone, an iodine-containing medication. However, iodine overdose leads to hypothyroidism, not thyrotoxicosis as in this case. Large amounts of iodine suppress the release of thyroxine from the thyroid gland, but the effect is transient.
Panic attacks (choice D) are a diagnosis of exclusion once other organic causes of palpitations and anxiety have been ruled out. In this patient's case, she is clearly hyperthyroid on physical exam, and a suppressed TSH confirms the diagnosis.
Choice E is incorrect since there is no evidence of self-administration of thyroid hormone and it is unclear why the patient would give the hormone to her son. In the entity Munchausen syndrome by proxy, caregivers create illness in their wards in order to attract attention and sympathy. In this case, the patient does not come to you seeking attention through her son's illness, and there is no prior history of similar behavior. Further, it does not explain how a community outbreak of similar illness could occur.
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