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  #1  
Old 10-20-2011
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A 26-year-old man is brought to the emergency department after being found by his family on his bathroom floor. He had apparently collapsed after being increasingly ill. His mother reports that over the last several weeks he has had severe insomnia, tremors, diarrhea, and fatigue. On arrival is only vaguely interactive and he does not follow commands appropriately. His blood pressure is 143/89, pulse is 125/min and his oxygen saturation is 96% on room air. On examination, he is diaphoretic and has a wide-eyed stare. He has a 2/6-midsystolic murmur at the second left intercostal space. His deep tendon reflexes are brisk throughout. Laboratory studies show:


Which of the following is the most appropriate next test to establish the etiology of this patient's collapse?



A.

24-hour urine for total catecholamines


B.

CT scan of the head


C.

Radioactive iodine uptake scan of the thyroid


D.

Serum thyrotropin-releasing hormone (TRH)


E.

Serum free triiodothyronine (T3) level
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  #2  
Old 10-20-2011
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I think i already answered this one not sure where

but its T3 lvls
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Old 10-20-2011
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E. Serum free triiodothyronine (T3) level
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Old 10-20-2011
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The correct answer is E. This patient is suffering from a severe bout of thyrotoxicosis, which is confirmed by his undetectable level of TSH. The surprising aspect of his presentation is the normal serum free T4. The most common causes of hyperthyroidism, Graves' disease and toxic multinodular goiter, both result in greatly increased production of T4. However, they can often have a proportionately greater increase in T3. Increased peripheral conversion of T4 to T3 may also play a role. In this patient's case, a solitary hyperfunctioning thyroid adenoma is secreting mostly T3, which is much more potent on target tissues than is T4. This condition, called T3 thyrotoxicosis, often occurs in the initial stages of hyperthyroidism, when symptoms are mild. However, it can also produce florid symptoms such as those seen above. The most appropriate next test to establish the etiology of this patient's collapse is the serum free T3 level.
A 24-hour urine for total catecholamines (choice A) is an appropriate initial test to screen for pheochromocytoma. Patients with these small, active tumors can present with tachycardia, mental status changes, and autonomic hyperactivity. However, their serum TSH levels will be normal, unlike this patient. The presence of a depressed TSH in the presence of hyperthyroid-like symptoms should always make the clinician suspect thyroid disease first.
A CT scan of the head (choice B), might be an appropriate study given his mental status changes. However, given what we know about the course of his illness and his laboratory results, imaging is unlikely to provide additional diagnostic information.
Radioactive iodine uptake scan of the thyroid (choice C), is a common test to evaluate the cause of hyperthyroidism. However, it often adds little to the history and physical examination and only serves to determine the appropriate dose for radioiodine ablation of the thyroid. For example, patients with Graves' disease will often have a family history of thyroid disease and will have a diffusely enlarged goiter. Patients with a solitary hyperfunctioning adenoma and such florid symptoms will invariably have a palpable nodule on physical examination. In this patient's case, the blood test is required first to confirm the diagnosis, and time cannot be spared to wait for a test as cumbersome as a thyroid uptake scan.
Serum TRH level (choice D), is rarely, if ever, useful in the evaluation of thyroid disease. The combined use of TSH, T4, and T3 studies makes this assay unnecessary, even when evaluating for "tertiary" or hypothalamic hyperthyroidism.
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