The association between TSH within the reference range and serum lipid concentrations in a population-based study....

Area of Science:

• Endocrinology
• Lipidology
• Public Health

Background:

• The relationship between thyroid function and serum lipids is complex.
• Normal thyroid function is typically defined by thyroid-stimulating hormone (TSH) levels within a reference range.
• Subclinical variations in thyroid function may impact metabolic health.

Purpose of the Study:

• To investigate the association between TSH levels and serum lipid concentrations in individuals without diagnosed thyroid disease.
• To determine if a linear relationship exists between TSH and lipids within the normal TSH reference range.

Main Methods:

• A cross-sectional, population-based study involving 30,656 participants.
• General linear models were used to analyze mean lipid concentrations (total cholesterol, LDL, non-HDL, HDL, triglycerides) across TSH categories.
• Participants were screened to exclude known thyroid disease.

Main Results:

• A significant linear trend was observed: as TSH increased within the normal range, total cholesterol, LDL, non-HDL cholesterol, and triglycerides increased (P < 0.001).
• HDL cholesterol showed a significant linear decrease with increasing TSH (P < 0.001).
• Associations varied by age and sex, with stronger links between TSH, triglycerides, and HDL cholesterol in overweight individuals.

Conclusions:

• Increasing TSH levels within the clinically normal range are associated with less favorable serum lipid profiles.
• The observed linear association between TSH and lipids suggests a continuous relationship, even below the threshold for overt thyroid dysfunction.
• These findings highlight the importance of monitoring lipid profiles in individuals with normal TSH levels.