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Difficulty: EasyMedical History Evaluation

A 29-year-old female medical resident presents to the employee health clinic with a 3-week history of unintentional weight loss, palpitations, and generalized anxiety. Physical examination reveals a resting heart rate of 110/min, a fine tremor in her outstretched hands, and a normal-sized, non-tender thyroid gland. Laboratory studies demonstrate a markedly suppressed thyroid-stimulating hormone (TSH) level and an elevated free thyroxine (T4) level. A subsequent radioactive iodine uptake scan reveals near-zero uptake. Which of the following historical inquiries is most essential to establishing the etiology of this patient's condition?

  1. Current use of unprescribed or over-the-counter thyroid hormone preparationsAnswer
  2. B
    Family history of autoimmune hyperthyroidism
  3. C
    Recent symptoms of a painful viral neck infection
  4. D
    Recent administration of iodinated intravenous contrast
  5. E
    Dietary history of insufficient iodine consumption

Answer

The correct answer is inquiring about the current use of unprescribed or over-the-counter thyroid hormone preparations.
The patient's presentation of thyrotoxicosis with a normal-sized, non-tender thyroid gland and near-zero radioactive iodine uptake is highly suspicious for exogenous thyroid hormone ingestion (factitious thyrotoxicosis). The fact that she is a medical resident provides a classic epidemiological clue for this condition. Therefore, directly inquiring about her use of unprescribed thyroid hormone preparations is the most critical element of the medical history to establish the diagnosis.

Step-by-Step Solution

1
Identify the clinical syndrome from the patient's symptoms and initial labs.
The patient has overt thyrotoxicosis (weight loss, palpitations, tremor, suppressed TSH, elevated free T4).
Establishing the biochemical state is the first step in diagnosing thyroid dysfunction.
2
Interpret the radioactive iodine uptake (RAIU) scan results.
Near-zero uptake indicates the thyroid gland is not actively synthesizing hormone.
This critically rules out causes of endogenous overproduction, such as Graves disease and toxic nodular goiter.
3
Differentiate among causes of low-uptake thyrotoxicosis.
The primary differential includes thyroiditis (typically painful or postpartum) and exogenous thyroid hormone ingestion.
Narrowing the differential diagnosis focuses the necessary historical evaluation.
4
Synthesize physical exam findings and demographic clues.
A non-tender, normal-sized thyroid in a healthcare professional with low RAIU strongly suggests factitious thyrotoxicosis.
Medical professionals have increased access to and knowledge of thyroid hormone, making surreptitious use a classic board presentation.
5
Determine the most critical historical inquiry to confirm the diagnosis.
Asking specifically about the use of unprescribed or over-the-counter thyroid hormone is essential.
The diagnosis of factitious thyrotoxicosis relies heavily on obtaining this specific medication history.

Key Concept

Factitious thyrotoxicosis presents with clinical hyperthyroidism, suppressed TSH, elevated thyroid hormones, a non-tender thyroid gland, and near-zero radioactive iodine uptake. Establishing the diagnosis requires targeted medical history evaluation regarding exogenous hormone use.
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Topics

Medical History Evaluation

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