The Association Between Normal Range TSH and Lipid Profile.

Area of Science:

• Endocrinology
• Metabolic Disorders
• Clinical Chemistry

Background:

• Dyslipidemia is often linked to thyroid dysfunction, particularly subclinical disorders.
• The precise role of thyrotropin (TSH) in dyslipidemia remains unclear.
• Thyrotropin levels are a primary focus in understanding thyroid-related lipid abnormalities.

Purpose of the Study:

• To investigate the correlation between normal range thyrotropin (TSH) levels and lipid profiles.
• To determine if variations in TSH within the euthyroid state impact lipid parameters.
• To assess the clinical significance of TSH's effect on dyslipidemia.

Main Methods:

• Analysis of 3,020 euthyroid subjects from the Tehran Thyroid study across three phases.
• Subjects categorized into four TSH quartiles (Q1-Q4) based on TSH levels.
• General Linear model used to assess correlations between TSH quartiles and lipid profiles (TC, LDL-C, TG, HDL-C).

Main Results:

• Mean total cholesterol (TC) and LDL-C, and median triglycerides (TG) were higher in the lowest TSH quartile (Q1).
• After six years, most lipid parameters significantly varied across TSH groups, with highest TC, TG, and HDL-C in the highest TSH quartile (Q4).
• Differences in lipid parameters within the middle normal TSH range were not significant, and effects were not clinically significant.

Conclusions:

• Normal range TSH levels exert a statistically significant influence on lipid profiles.
• The observed effects of TSH on lipid parameters within the normal range are not clinically significant.
• Further research may be needed to fully elucidate the complex relationship between TSH and dyslipidemia.