Review Question - QID 221248

This patient with symptoms of hyperthyroidism, decreased TSH, elevated free T4, and several thyroid nodules with increased iodine uptake most likely has a toxic multinodular goiter.

Toxic multinodular goiters are benign thyroid tumors resulting from hyperplasia of thyroid follicular cells, producing increased amounts of triiodothyronine (T3) and thyroxine (T4). They most often occur in younger patients and are slow-growing. Patients will present with signs of hyperthyroidism including anxiety, palpitations, heat intolerance, weight loss, and oligomenorrhea in women. On exam, non-tender palpable nodules will often be present. Laboratory studies will show decreased TSH and increased T3 and T4. To distinguish this diagnosis from other causes of hyperthyroidism, an RAIU is often done. A toxic adenoma will reveal several localized areas of uptake of radioactive iodine. Patients with overt hyperthyroidism due to a toxic multinodular goiter require treatment. This includes symptomatic relief with beta-blockers, radioiodine ablation, surgery, or suppressive thioamide therapy.

Shim et al. review cancer risk after radioactive iodine treatment for hyperthyroidism. They found that there was no evidence of increased cancer risk after exposure to radioiodine in general; however, there was a dose-dependent increased risk for thyroid cancer. They recommend that primary care clinicians pay attention to the RAI dosages received by their hyperthyroid patients.

Figure/Illustration A is a radioactive iodine uptake (RAIU) test of the thyroid gland showing several areas of focal uptake (red circles). This finding is consistent with a toxic multinodular goiter.

Incorrect Answers:
Answer 1: Grave disease is the most common cause of hyperthyroidism. It is an autoimmune disorder resulting from TSH receptor antibodies that overstimulate thyroid hormone synthesis and release. Patients will often present with a diffusely enlarged thyroid gland, extrathyroidal manifestations (pretibial myxedema and exophthalmos), and diffusely increased radioactive iodine uptake on RAIU.

Answer 2: Hashimoto thyroiditis is a chronic autoimmune thyroiditis that results in a painless goiter. Although it can rarely manifest as hyperthyroidism, Hashimoto thyroiditis is the most common cause of hypothyroidism in non-iodine-deficient areas. Diagnosis can be made by testing for antithyroid antibodies.

Answer 3: Subacute thyroiditis (de Quervain thyroiditis) is a self-limited inflammatory disease of the thyroid gland that can cause transient hyperthyroidism. The patient will have a tender goiter and RAIU will show decreased radioiodine uptake.

Answer 5: Toxic thyroid adenoma would present very similarly to toxic multinodular goiter; however, the RAIU test will demonstrate a single focal area of increased uptake.

Bullet Summary:
A toxic adenoma is a benign tumor that will present with hyperthyroidism, a nontender palpable nodule, and focal uptake on radioactive iodine uptake.