Is total body scintigraphy necessary now given the patient's severe hypothyroidism (elevated Thyroid-Stimulating Hormone (TSH)) and not yet started on Euthyrox (levothyroxine)?

From the Guidelines

No, total body scintigraphy should not be performed while the patient has severe hypothyroidism with elevated TSH levels and before starting levothyroxine (Euthyrox) therapy. The patient should first be treated with levothyroxine to achieve a euthyroid state before undergoing scintigraphy. Typically, levothyroxine should be initiated at an appropriate dose based on the patient's weight, age, and comorbidities (usually starting at 25-50 mcg daily for elderly or cardiac patients, or 1.6 mcg/kg/day for others), with dose adjustments every 4-6 weeks until TSH normalizes. Once the patient is euthyroid, they would need to discontinue levothyroxine for 2-4 weeks before undergoing scintigraphy. This sequence is important because elevated TSH stimulates thyroid tissue uptake of radiotracer, which can lead to increased background uptake and potentially mask abnormalities. Additionally, untreated hypothyroidism can affect the biodistribution of the radiotracer, potentially leading to false-positive or false-negative results. Treating the hypothyroidism first will ensure more accurate and interpretable scintigraphy results. According to the American College of Radiology, whole-body scintigraphy has no role in certain thyroid disease evaluations, as stated in the 2019 guidelines 1.

Some key points to consider in this scenario include:

• The need to achieve a euthyroid state before scintigraphy to ensure accurate results
• The potential for elevated TSH to interfere with radiotracer uptake and interpretation
• The importance of discontinuing levothyroxine for a period before scintigraphy to avoid interference with the test.

Given the potential for severe hypothyroidism to impact the accuracy and interpretation of total body scintigraphy, initiating levothyroxine therapy and achieving a euthyroid state is crucial before proceeding with scintigraphy. This approach prioritizes the patient's morbidity, mortality, and quality of life by ensuring that any subsequent diagnostic tests are accurate and reliable.

From the Research

Total Body Scintigraphy in Severe Hypothyroidism

• The patient's severe hypothyroidism is indicated by an elevated Thyroid-Stimulating Hormone (TSH) level of 100, and they have not yet started on Euthyrox (levothyroxine) 2.
• There is no direct evidence in the provided studies to suggest that total body scintigraphy is necessary in this case.
• The studies focus on the treatment of hypothyroidism with levothyroxine, the efficacy of different dosage regimens, and the challenges in interpreting TSH results 2, 3, 4, 5, 6.

Treatment of Hypothyroidism

• The treatment of choice for hypothyroidism is levothyroxine sodium, which is effective in normalizing TSH levels and resolving symptoms in most patients 4, 5, 6.
• Some studies suggest that combined therapy with levothyroxine and liothyronine may be beneficial for certain patients, but the evidence is not conclusive 4, 5, 6.
• The decision to start treatment with levothyroxine should be based on the patient's clinical presentation, TSH levels, and other relevant factors 2, 3.

Diagnostic Considerations

• TSH levels are influenced by various factors, including concomitant diseases, medications, and lifestyle factors, which should be taken into account when interpreting results 3.
• The upper limit of the TSH reference range is a matter of debate, and treatment decisions should be individualized based on the patient's specific circumstances 3.