Serum T3 level in the patients with hyperthyroidism after therapy

Area of Science:

• Endocrinology
• Thyroidology
• Clinical Chemistry

Background:

• Thyroid hormones, triiodothyronine (T3) and thyroxine (T4), are crucial for metabolic regulation.
• Assessing thyroid function typically involves measuring serum T4 and T3 levels.
• Radioiodine therapy and anti-thyroid drugs are common treatments for hyperthyroidism.

Purpose of the Study:

• To evaluate the diagnostic and prognostic utility of serum T3 levels in various thyroid diseases.
• To compare the sensitivity of serum T3 and T4 measurements in monitoring thyroid function post-treatment.
• To identify potential indicators for predicting hyperthyroidism recurrence.

Main Methods:

• Serum T3 levels were measured using the Dainabot kit for T3 RIA in unextracted serum.
• Thyroid function was assessed in normal, hyperthyroid, and hypothyroid patient groups.
• Serum T3 and T4 levels were monitored over time following radioiodine therapy for hyperthyroidism.

Main Results:

• Serum T3 levels were significantly elevated in hyperthyroid patients (5.7 +/- 3.5 ng/ml) and decreased in hypothyroid patients (undetectable to 0.8 ng/ml) compared to normal subjects (0.8-1.6 ng/ml).
• Post-radioiodine therapy, serum T3 and T4 generally decreased in parallel, but some patients exhibited 'T3-toxicosis' with high T3 despite normalized T4, indicating a risk of recurrence.
• In euthyroid states post-treatment, the ratio of serum T3 levels (pre- to post-treatment) decreased more significantly than the T4 ratio, suggesting T3 is a more sensitive marker.

Conclusions:

• Serum T3 is a more sensitive index of thyroid function than serum T4 in euthyroid states after radioiodine or anti-thyroid drug therapy.
• The serum T3 level and the T4/T3 ratio are valuable for estimating the prognosis of hyperthyroid patients after various treatments.
• Monitoring serum T3 levels can aid in identifying patients at risk for hyperthyroidism recurrence.