Approach to hyperthyroidism and thyrotoxicosis: Clinical sciences

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Introduction0:00–0:41

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.

Unstable Patient0:41–2:00

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.

Stable Patient2:00–2:39

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.

Alternative diagnosis2:39–2:57

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!

Primary Hyperthyroidism 2:57–3:37

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.

RAIU scan - normal/elevated3:37–4:33

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.

RAIU scan - low4:33–7:04

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.
Subacute thyroiditis is usually preceded by an upper respiratory infection, and a key clinical finding is a tender thyroid on palpation.
Typically, patients with thyroiditis experience an initial hyperthyroid phase, which is due to the release of preformed thyroid hormones from damaged thyroid cells.
The initial hyperthyroid phase is followed by a hypothyroid phase after thyroid hormone levels are depleted, and finally, a recovery phase, in which thyroid function is restored.Here’s a high yield fact!
Hashimoto thyroiditis is the most common cause of hypothyroidism, and it’s caused by autoimmune destruction of thyroid cells by antithyroid antibodies.
In the early stages of the disease, hashitoxicosis can occur, because when a lot of cells are destroyed at once, they can release preformed thyroid hormones into the circulation, causing hyperthyroidism.
On the other hand, if the thyroglobulin level is low, and ESR is normal, consider hyperthyroidism due to medication effects.
Some common medications associated with hyperthyroidism include levothyroxine, iodine taken at excessive doses, and amiodarone.
If there is causative medication identified, you can diagnose medication-induced hyperthyroidism. However, if there are no causative medications and the rest of the workup is inconclusive, you can diagnose idiopathic hyperthyroidism.Now, here’s a clinical pearl to keep in mind!
Iodine excess is a well-known cause of hyperthyroidism, since iodine is the precursor for thyroid hormone production. Since amiodarone has a high iodine content, it can cause thyrotoxicity manifesting as hyperthyroidism.
Paradoxically, and for reasons which are unclear, iodine excess can also trigger hypothyroidism, which is seen most commonly in individuals with autoimmune thyroiditis.Let’s go all the way back to our lab results.

Secondary hyperthyroidism7:04–7:34

If both the TSH and free T4 are high, you can diagnose secondary hyperthyroidism, also known as central hyperthyroidism.
This type of hyperthyroidism is usually caused by a lesion in the pituitary gland, such as a TSH-secreting pituitary adenoma.
This is a rare condition, but if suspected, it’s important to get an MRI of the head to evaluate for a pituitary mass, and also assess other pituitary hormone levels for deficiencies!Now, let’s go back one last time!

Subclinical hyperthyroidism7:34–8:26

If your patient has low TSH and low or normal free T4, you can diagnose subclinical hyperthyroidism. These individuals are typically mildly symptomatic or even completely asymptomatic, so the diagnosis is most often based on abnormal lab findings detected via routine screening of thyroid function.Now, here’s a clinical pearl to keep in mind!
Subclinical hyperthyroidism can be an early finding in toxic multinodular goiter and Graves disease, and can have the same adverse effects as overt hyperthyroidism, such as increased risk of cardiovascular events and decreased bone mineral density.
Since subclinical hyperthyroidism can progress to overt disease over time, be sure to follow up with thyroid function tests every 2 to 6 months!Alright, as a quick recap… When suspecting hyperthyroidism or thyrotoxicosis, your first step is to check TSH and free T4.

Review8:26–9:34

If TSH is low and free T4 is high, diagnose primary hyperthyroidism and order TSH Receptor antibodies. If these are present, diagnose Graves disease, but if not, order a radioactive iodine uptake scan!
If the uptake is elevated… think of Graves disease, toxic multinodular goiter, or toxic adenoma, depending on the uptake pattern.
On the flip side, if uptake is low, order thyroglobulin levels, and if they’re high in the setting of a suggestive clinical picture, diagnose subacute thyroiditis.
However, if thyroglobulin levels are low, consider medication-induced hyperthyroidism or idiopathic hyperthyroidism. Finally, if both TSH and free T4 are high, you can diagnose secondary hyperthyroidism, but if there’s low TSH and low or normal free T4,