Metabolic and hepatic differences among biochemically euthyroid individuals with distinct thyroid hormone sources: a...

Area of Science:

• Endocrinology
• Hepatology
• Metabolic Health

Background:

• Thyroid hormone profiles and their ratios, such as T3/T4, are crucial for metabolic regulation.
• Hepatic steatosis and fibrosis are significant health concerns with complex etiologies.
• Understanding the interplay between thyroid function and liver health is vital, even in biochemically euthyroid states.

Purpose of the Study:

• To investigate the associations between thyroid hormone profiles (including T3/T4 ratio), body composition, and markers of hepatic steatosis and fibrosis.
• To compare these associations in individuals with different thyroid physiologies: Hashimoto's thyroiditis (HT), post-total thyroidectomy (TT), and healthy controls (C), all within the euthyroid range (normal TSH).

Main Methods:

• A retrospective, cross-sectional study included 123 HT patients, 103 TT patients, and 83 healthy controls, all with TSH within the reference range.
• Assessed thyroid hormone levels and ratios (T3/T4, T3/TSH, T4/TSH), anthropometric measurements, body composition, and non-invasive liver fibrosis (FIB-4) and steatosis (FLI) indices.

Main Results:

• The T3/T4 ratio significantly differed across groups (C > HT > TT).
• Both HT and TT groups showed higher FLI and FIB-4 scores compared to controls.
• In TT patients, the T3/T4 ratio independently predicted FIB-4 after adjusting for age and visceral adiposity, while body composition parameters did not.

Conclusions:

• Thyroid hormone balance is complex, with distinct functional capacities even in biochemically euthyroid individuals.
• Differences in thyroid hormone ratios can have significant metabolic and hepatic consequences.
• Thyroid hormone ratios may offer valuable clinical insights for a tissue-oriented evaluation of the thyroid-liver axis.