Review Question - QID 210471

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Hypothyroidism vs. Hyperthyroidism Studies QID: 210471 (M2.EC.18.4869)

QID 210471 (Type "210471" in App Search)

A 48-year-old woman is brought to the emergency department per her psychiatrist's recommendation. She has been more restless than her baseline over the past week. The patient feels her mind is racing. Her medical history is significant for bipolar disorder on lithium and type 1 diabetes mellitus. The family and the patient both note that the patient has been taking her medications. She denies any recent illness or sick contacts. Her temperature is 100°F (37.8°C), blood pressure is 100/60 mmHg, pulse is 130/min, and respirations are 20/min. She appears diaphoretic, and her cardiac exam is notable for an irregularly irregular rhythm with a 2/6 early systolic murmur. Blood counts and metabolic panel are within normal limits. The patient's lithium level is within the therapeutic range. Which of the following test should be ordered?

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Thyroglobulin level

1/49

Thyroid stimulating hormone and free thyroxine levels

78%

38/49

Thyroid stimulating hormone and total thyroxine levels

10%

5/49

Thyrotropin-releasing hormone stimulation test

0/49

Triiodothyronine and thyroxine levels

1/49

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This patient with bipolar disorder on lithium is presenting with restlessness in the setting of atrial fibrillation and diaphoresis. Hyperthyroidism needs to be evaluated using TSH and free T4 levels.

Hyperthyroidism is an elevated level of thyroid hormones caused by increased synthesis of thyroid hormones, excess release of preformed thyroid hormones, or an endogenous or exogenous extrathyroidal source. Lithium normally suppresses thyroid hormone production, causing hypothyroidism, but rare cases of lithium-associated thyrotoxicosis have been described. The TSH test has the highest sensitivity and specificity for hyperthyroidism. Free thyroxine (T4) and total triiodothyronine (T3) levels can be obtained subsequently or simultaneously depending on clinical suspicion.

Ross et al. review the evidence regarding the diagnosis and treatment of hyperthyroidism. They discuss how there are many etiologies of this disease including Grave disease. They recommend measuring TSH and free T4 levels in order to distinguish between these etiologies.

Incorrect Answers:
Answer 1: Thyroglobulin levels are used to evaluate the effectiveness of thyroid cancer treatment. Increased levels can suggest hyperthyroidism but do not necessarily correlate with increased thyroxine levels.

Answer 3: TSH and total thyroxine levels may be elevated without clinical evidence of hyperthyroidism because free thyroxine levels more accurately reflect the active amount of thyroxine. Changes in protein levels such as albumin will affect total thyroxine levels.

Answer 4: The thyrotropin-releasing hormone stimulation test is no longer offered clinically because of the effectiveness of TSH assessment to determine etiology. This historical test was used in order to determine the source of hyperthyroidism.

Answer 5: Triiodothyronine and thyroxine levels are insufficient to assess whether the hyperthyroidism is primary, secondary, or tertiary in etiology. This differential is made using TSH levels.

Bullet Summary:
TSH, free T4, and total T3 levels are used to evaluate the etiology of hyperthyroidism.