Examkin

Question

Difficulty: MediumDiagnostic Workup and Test Sequencing

A 48-year-old woman presents to the outpatient clinic reporting a newly discovered swelling in the right side of her neck that she noticed while looking in the mirror two weeks ago. Over the past month, she has also experienced intermittent heart palpitations and an unintentional 3-kg (6.6-lb) weight loss despite a normal appetite. She has no significant past medical history and takes no medications. Vital signs include a blood pressure of 130/80 mmHg, a heart rate of 105/min, and a temperature of 37.1°C (98.8°F). Physical examination reveals a 2.5-cm, firm, mobile, and non-tender nodule in the right thyroid lobe. No cervical lymphadenopathy is appreciated.

Laboratory testing reveals:
Thyroid-stimulating hormone (TSH): 0.05 µU/mL
Free thyroxine (T4): 2.1 ng/dL

A dedicated neck ultrasound confirms a 2.5-cm solid, hypoechoic nodule in the right lobe of the thyroid without microcalcifications or irregular margins.

What is the most appropriate next step in the diagnostic evaluation of this patient?

  1. A
    Computed tomography (CT) scan of the neck with contrast
  2. B
    Fine-needle aspiration biopsy of the nodule
  3. C
    Measurement of serum calcitonin levels
  4. Thyroid scintigraphyAnswer
  5. E
    Measurement of serum thyroglobulin levels

Answer

The most appropriate next step in the diagnostic evaluation of this patient is thyroid scintigraphy.
The correct answer is thyroid scintigraphy. The diagnostic workup of a newly discovered thyroid nodule begins with a serum TSH measurement and a neck ultrasound. If the TSH level is normal or elevated, the algorithm proceeds to fine-needle aspiration (FNA) based on sonographic features and size. However, if the TSH is suppressed (subnormal), as seen in this patient with signs of hyperthyroidism, the next step in diagnostic sequencing is a radionuclide thyroid scan (scintigraphy) using iodine-123 or technetium-99m. This test determines whether the nodule is hyperfunctioning ('hot') or nonfunctioning ('cold'). A 'hot' nodule is almost always benign, and FNA is generally not indicated; the patient is instead managed for hyperthyroidism. If the nodule is 'cold', the risk of malignancy is higher, and the workup proceeds to FNA.

Step-by-Step Solution

1
Evaluate the clinical presentation and physical exam.
The patient has signs of thyrotoxicosis (palpitations, weight loss, tachycardia) and a 2.5-cm thyroid nodule.
This establishes the presence of a palpable structural abnormality of the thyroid gland accompanied by hypermetabolic symptoms.
2
Analyze the initial diagnostic tests (TSH and ultrasound).
TSH is significantly suppressed (0.05 µU/mL) with elevated free T4, confirming primary hyperthyroidism. The ultrasound confirms a solid nodule meeting size criteria for further workup.
The initial step for any thyroid nodule >1 cm is to check TSH and perform an ultrasound. The TSH level dictates the subsequent sequencing.
3
Determine the next diagnostic step based on the suppressed TSH.
A radionuclide thyroid scan (scintigraphy) is indicated.
Because the TSH is low, it is necessary to determine if the nodule is autonomously producing the excess hormone (a 'hot' nodule). Hot nodules are rarely malignant, meaning invasive testing can usually be avoided.

Key Concept

The initial evaluation of a thyroid nodule requires measuring TSH; if the TSH is suppressed, the appropriate next step is thyroid scintigraphy to evaluate for a hyperfunctioning ('hot') nodule.
Estimated Time:1m 15s
Rate this question

Topics

Diagnostic Workup and Test Sequencing

More questions from this topic