Review Question - QID 214776

This patient has toxic multinodular goiter as demonstrated by her symptoms of hyperthyroidism (i.e., weight loss and increased appetite), laboratory values (i.e., low TSH and high free T4), and RAIU findings (i.e., areas of diminished and increased uptake).

Toxic multinodular goiter is a common benign cause of hyperthyroidism, second in prevalence only to Graves disease. It is due to focal and/or diffuse hyperplasia of thyroid follicular cells. These cells' functional capacity is independent of regulation by thyroid-stimulating hormone and thus produce high levels of thyroid hormones (e.g., T3/T4) in the setting of low TSH. Patients often present with symptoms of hyperthyroidism including heat intolerance, hyperactivity, tremor, irritability, weight loss, increased appetite, tachycardia, and tracheal compression. Physical examination often reveals a palpable nodular goiter. Laboratory abnormalities include high free T4, low TSH (secondary to negative feedback), and negative/normal anti-thyroid peroxidase antibodies. Thyroid ultrasound usually shows multiple nodules and typically 1 or more focal areas of increased uptake on RAIU. Nonfunctioning (“cold”) nodules may be also present in some patients and should be further evaluated with fine-needle aspiration (FNA) based on size and the presence of suspicious ultrasound characteristics. Treatment usually involves antithyroid medications such as propylthiouracil or methimazole, radioactive iodine, or surgery.

Knobel et al. studied standards of care for the diagnosis and treatment of non-toxic goiters. The authors found that the development of goiters is associated with iodine deficiency, an increase in serum thyroid-stimulating hormone (TSH) levels, natural goitrogens, smoking, and a lack of selenium and iron intake. The authors recommend that diagnostic workup of non-toxic goiters should include measurement of TSH, accurate imaging with high-resolution ultrasonography or computed tomography, and fine-needle aspiration biopsy.

Figure/Illustration A is a radioactive iodine uptake test demonstrating focal areas of increased uptake (“hot” nodule, arrows) and areas of decreased uptake (“cold” nodule, chevron) characteristic of toxic multinodular goiter.

Incorrect Answers:
Answer 1: Graves disease is the most common cause of hyperthyroidism in the developed world. It is an autoimmune disorder secondary to the presence of thyroid-stimulating immunoglobulin (TSI), which has a similar effect to TSH, and subsequent excess production of thyroid hormones. Patients with Graves disease often have similar laboratory abnormalities (e.g., low TSH and high free T4). However, on RAIU scans, patients will have diffusely increased uptake.

Answer 2: Thyroid lymphoma is rare and predominantly affects patients over 70 years old. It classically presents as a rapidly enlarging neck mass that often results in hoarseness, dysphagia, and signs of tracheal compression (e.g., breathing difficulties) on initial presentation. Patients usually have elevated lymphocytes in laboratory studies, which is not the case in this patient.

Answer 3: Papillary thyroid cancer is the most common type of thyroid cancer and commonly occurs in women between the ages of 20-55. It is usually discovered on routine examination as an asymptomatic thyroid nodule and is diagnosed via fine-needle aspiration. The lesion demonstrates decreased uptake on RAIU scans as opposed to increased uptake seen in toxic multinodular goiter.

Answer 4: Subacute thyroiditis is a form of thyroiditis that initially presents with a period of thyrotoxicosis and subsequent hypothyroidism. It most commonly follows an upper respiratory tract infection and is believed to be secondary to viral infections. Patients often present with sudden and painful enlargement of the thyroid gland with fever, malaise, and muscle aches. Although this patient reports a recent upper respiratory infection (URI), her symptoms were present long before the infection, and her thyroid nodule was non-tender.

Bullet Summary:
Toxic multinodular goiter usually presents with symptoms of hyperthyroidism and focal areas of increased uptake (“hot nodules”) on radioactive iodine uptake testing.