Abnormalities of thyroid function tests in hospital inpatients.

Area of Science:

• Endocrinology
• Internal Medicine
• Clinical Chemistry

Background:

• Thyroid function tests are vital for diagnosing thyroid disorders.
• Euthyroid patients with non-thyroidal illnesses may exhibit altered thyroid hormone levels.
• Previous hypotheses suggested albumin or fatty acids influence free thyroxine levels in these patients.

Purpose of the Study:

• To analyze thyroid function test results in clinically euthyroid inpatients.
• To investigate the prevalence of abnormal thyroid hormone levels in euthyroid patients.
• To determine the correlation between free thyroxine and other thyroid hormones, binding proteins, and non-thyroidal factors.

Main Methods:

• Analysis of thyroid function tests (total T3, free T3, total T4, free T4, TBG ratio) in 199 euthyroid inpatients.
• Statistical analysis to identify correlations between various thyroid hormone parameters.
• Assessment of correlations with serum albumin and non-esterified fatty acids.

Main Results:

• A significant percentage of euthyroid patients showed low total triiodothyronine (61.8%), free triiodothyronine (57.8%), total thyroxine (21.1%), and free thyroxine (17.6%).
• Positive correlations were observed between free thyroxine and total thyroxine, T4/TBG ratio, and free triiodothyronine (P < 0.001).
• No correlation was found between free thyroxine and serum albumin or non-esterified fatty acids, refuting previous hypotheses.

Conclusions:

• Low free thyroxine in euthyroid patients with non-thyroidal illnesses is not consistently explained by reduced albumin or increased fatty acids.
• Thyroid stimulating hormone (TSH) measurements are essential for accurately diagnosing hypothyroidism in these patients.
• Relying solely on free thyroxine levels can be misleading in the assessment of thyroid status in non-thyroidal illnesses.