Approach to hyperthyroidism and thyrotoxicosis: Clinical sciences

Hyperthyroidism refers to any condition in which thyroid hormone levels are inappropriately high, which increases the basal metabolic rate and potential thyroid hormone toxicity. Patients with hyperthyroidism present with a wide spectrum of signs and symptoms, which can range from subclinical disease to severe life-threatening conditions, like thyrotoxicosis. The diagnostic workup for hyperthyroidism mainly involves checking a thyroid-stimulating hormone, or TSH level, and a free thyroxine, or free T4 level, to determine whether your patient has primary, secondary, or subclinical hyperthyroidism.

Now, if your patient presents with chief concerns suggesting hyperthyroidism or thyrotoxicosis, you should first perform an ABCDE assessment to determine if your patient is unstable. If unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access and put your patient on continuous vital sign monitoring, including heart rate, blood pressure, and pulse oximetry, as well as cardiac telemetry. Additionally, provide supplemental oxygen if the saturation is below 90%.

If your patient presents with fever, tachycardia, delirium, or coma, you should suspect thyrotoxic crisis, also called thyroid storm. This is a severe, life-threatening presentation that typically occurs in patients with untreated or undertreated hyperthyroidism, and it’s triggered by an inciting event, such as major illness or surgery.

Treatment includes the four Ps: Propranolol or other beta-blockers, Propylthiouracil, Prednisolone or other glucocorticoids, and Potassium iodide. These patients need close monitoring, and may require intensive measures such as volume resuscitation and whole-body cooling.

Alright, now that we're done with unstable patients, let’s go back to the ABCDE assessment and discuss the stable ones. First, obtain a focused history and physical examination. Your patient will likely report symptoms suggesting a high basal metabolic rate and sympathetic activity. These may include palpitations, heat intolerance, increased appetite and unintentional weight loss, as well as increased bowel movement frequency or diarrhea. On the flip side, physical examination findings typically include tachycardia; tremor; warm, moist skin; and muscle weakness.

At this point, you should consider hyperthyroidism, so your next step is to order a TSH and free T4. Normal TSH and free T4 reflect euthyroidism, which means the thyroid works properly, so you should consider alternative diagnoses.

Now, switching gears and going back to TSH and free T4! If the TSH is low and the free T4 is high, diagnose primary hyperthyroidism, and order TSH Receptor antibodies or TRAb for short. If antibodies are present, diagnose Graves disease. However, although most patients with Graves disease will have detectable levels of antibodies, keep in mind that they can have undetectable antibodies in some cases! On the flip side, if the thyrotropin antibodies are not present, order a radioactive iodine uptake scan of the thyroid.

If the uptake is normal or elevated, your next step is to assess the pattern of uptake. Diffuse uptake throughout the gland is diagnostic of Graves disease, even with undetectable antibodies. Alternatively, if there’s focal uptake of radioactive iodine in multiple areas of the thyroid gland, diagnose toxic multinodular goiter, and if there’s focal uptake in only one area of the thyroid gland, diagnose toxic adenoma.

And, here’s a high-yield fact to keep in mind! Struma ovarii is a rare ovarian teratoma that consists mainly of ectopic thyroid tissue, so these patients may present with signs and symptoms of hyperthyroidism. Diagnosis can be confirmed with iodine-123 scintigraphy, which reveals higher uptake in the ovarian mass compared with the thyroid gland.

Alright, now let’s go back and discuss cases in which the radioactive iodine uptake is low. In these patients, you should order a thyroglobulin level, as well as an ESR. If there’s high thyroglobulin and ESR, in the setting of a suggestive clinical picture, you can diagnose subacute thyroiditis.