A 36-year-old woman is found to have a thyroid nodule during a routine physical examination. She has had no heat or cold intolerance, skin changes, or fatigue. Her appetite and stooling habits have not changed, and her weight is stable. Menstrual cycles are regular with no excessive bleeding. The patient has no other medical conditions and takes no medications. She has had no prior radiation exposure. Family history is negative for thyroid disorders. The patient does not use tobacco, alcohol, or illicit drugs. She is an architect at a construction firm. Temperature is 36.7 C (98 F), blood pressure is 130/80 mm Hg, pulse is 80/min, and respirations are 16/min. Physical examination shows no abnormalities with the exception of a 1-cm, discrete, nontender, and firm nodule in the left thyroid lobe. Which of the following is the most appropriate next step in management of this patient?
Show Explanatory Sources
Thyroid nodules are common and may be diagnosed on physical examination or noted incidentally when imaging studies are obtained for other reasons. Once a thyroid nodule is found, cancer risk factors (family history, radiation exposure) should be assessed by history. Physical examination should evaluate the size, mobility, and firmness of the thyroid nodule and whether enlarged cervical lymph nodes are present.
Serum TSH levels should be obtained, along with a thyroid ultrasound to determine nodule size and sonographic features. Certain sonographic features (microcalcifications, irregular margins, internal vascularity) carry a much higher risk of malignancy than others (cystic or spongiform lesions). Thyroid nodules >1 cm with these high-risk sonographic features—and all noncystic thyroid nodules >2 cm—should undergo fine-needle aspiration (FNA) biopsy.
If the TSH is low (eg, hyperthyroid), the patient should be evaluated with radionuclide thyroid scan using iodine-123 (Choice C). A hyperfunctioning ("hot") nodule (increased isotope uptake in the nodule with decreased surrounding uptake) is associated with a low cancer risk; a hypofunctioning ("cold") nodule (decreased isotope uptake compared to surrounding tissue) is associated with a higher risk of cancer.
(Choice A) Anti–thyroid peroxidase antibody testing can identify chronic autoimmune (Hashimoto) thyroiditis in patients with high TSH levels. It does not differentiate between benign and malignant lesions.
(Choice B) A CT scan is inferior to ultrasound in characterizing thyroid nodules. In fact, even if a thyroid nodule is detected on CT scan, the patient would still need an ultrasound of the thyroid. A CT scan may be helpful for surgical planning if there is retrosternal extension of the gland or there are surrounding structures or lymph nodes involved.
(Choice D) Although most thyroid nodules are benign, investigation with TSH and ultrasound is still required to ensure the risk of malignancy is low.
(Choice E) Calcitonin is an important tumor marker in medullary thyroid carcinoma. Testing for calcitonin should be performed if there is suspicion for medullary thyroid carcinoma based on family history or FNA findings.
(Choice F) In a patient with an intact thyroid gland, thyroglobulin testing is not useful because it can be elevated in many thyroid conditions and does not differentiate between benign and malignant lesions. Serum thyroglobulin is useful as a tumor marker for patients who have had a total thyroidectomy for papillary or follicular thyroid carcinoma.
Educational objective:
Thyroid nodules should be evaluated by serum TSH and ultrasound. A radionuclide scan is indicated only for patients with low TSH.