Color Doppler ultrasound and real-time elastography in patients with hypothyroidism for the prediction of levothyroxine replacement: a cross-sectional study of 338 patients.

The study enrolled 338 hypothyroid patients, the majority of whom had autoimmune thyroiditis as the underlying cause.

• 85.2% of enrolled patients had autoimmune thyroiditis (AT)
• Exclusion criteria comprised specific medical conditions, medication history, and nodular abnormalities of the thyroid gland
• Patient demographics recorded included age, sex, and BMI
• Treatment parameters (LT4 daily dose) and thyroid hormone levels (TSH, fT4) were recorded

Suboptimal levothyroxine replacement was observed in approximately one-fifth of patients at the time of enrollment.

• Suboptimal LT4 replacement was observed in 20.1% of patients at the time of enrollment
• This finding was assessed across both autoimmune and non-autoimmune hypothyroid subgroups
• LT4 dose/BMI ratio was used as an indicator of severity of hypothyroidism

Patients with autoimmune thyroiditis had increased elastography ratios compared to those without autoimmune disease.

• Autoimmune thyroiditis patients showed increased elastography ratios relative to non-autoimmune hypothyroid patients
• A positive association between elastography ratios and vascularity was found in autoimmune thyroiditis patients
• Real-time elastography was used as part of the imaging protocol alongside color Doppler ultrasound

In patients without autoimmune thyroiditis, those with suboptimal LT4 replacement had lower total thyroid volume.

• This association between suboptimal LT4 replacement and lower thyroid volume was specific to the non-autoimmune subgroup
• Total thyroid volume was among the ultrasound parameters systematically assessed
• The finding suggests different structural correlates of suboptimal treatment depending on disease etiology

Patients with suboptimal LT4 replacement had higher peak systolic velocity and end-diastolic velocity in the inferior thyroid artery and lower resistive index.

• Higher PSV and EDV in the inferior thyroid artery were found in suboptimal LT4 replacement patients
• Lower resistive index (RI) was also observed in patients with suboptimal LT4 replacement
• These Doppler flow parameters were measured in both superior and inferior thyroid arteries
• The pattern of higher velocity and lower resistance suggests increased thyroid blood flow in undertreated hypothyroidism

The severity of hypothyroidism as indicated by LT4 dose/BMI was negatively correlated with thyroid volume and EDV values of both superior and inferior thyroid arteries.

• LT4 dose/BMI ratio served as a proxy measure for severity of hypothyroidism
• Negative correlations were found between LT4 dose/BMI and thyroid volume
• Negative correlations were also found between LT4 dose/BMI and EDV values of both the superior and inferior thyroid arteries
• This suggests that more severe hypothyroidism is associated with smaller thyroid glands and lower diastolic flow velocities

PSV of the inferior thyroid artery can predict suboptimal LT4 replacement with a sensitivity of 81.8% and specificity of 42%.

• Sensitivity for predicting suboptimal LT4 replacement was 81.8%
• Specificity for predicting suboptimal LT4 replacement was 42%
• PSV of the inferior thyroid artery was identified as the key predictive Doppler parameter
• The authors suggest color Doppler ultrasound can serve as an alternative method to assess treatment responses and identify patients requiring further hormonal examinations when blood tests are challenging to obtain