Systemic Thyroid Hormone Status in Treated Graves' Disease.

Area of Science:

• Endocrinology
• Thyroidology
• Internal Medicine

Background:

• Graves' disease is an autoimmune disorder leading to hyperthyroidism.
• Treatment aims to restore normal thyroid hormone levels (euthyroidism).
• Levothyroxine (LT4) is used to treat hypothyroidism, including that resulting from Graves' disease treatment.

Purpose of the Study:

• To compare thyroid hormone status markers between treated euthyroid Graves' patients and levothyroxine (LT4)-treated hypothyroid Graves' patients.
• To investigate differences in the triiodothyronine to thyroxine ratio (T3:T4) and associated metabolic parameters.

Main Methods:

• Retrospective analysis of 277 Graves' disease patients divided into three groups: LT4-treated hypothyroid, methimazole (MMI)-treated euthyroid, and untreated euthyroid.
• Statistical analysis included correlation coefficients and univariate/multivariate linear regression models.
• Key hormone levels (fT4, T3, TSH), antibodies (TPOAb, TRAb), BMI, and lipid profiles were assessed.

Main Results:

• LT4-treated hypothyroid patients had a significantly lower serum T3:T4 ratio (27% lower) compared to euthyroid groups.
• Despite lower TSH, LT4-treated patients exhibited higher fT4 and lower T3, TPOAb, and TRAb levels.
• Elevated BMI, total cholesterol, LDL cholesterol, and lower HDL cholesterol were noted in the LT4-treated group.

Conclusions:

• Levothyroxine-treated hypothyroid Graves' patients demonstrate a distinct hormonal and metabolic profile.
• A lower T3:T4 ratio in LT4-treated patients suggests altered thyroid hormone economy despite normalized TSH.
• Differences in BMI and lipid parameters highlight potential long-term metabolic consequences.