Age-related changes in thyroid function: a longitudinal study of a community-based cohort.

Area of Science:

• Endocrinology
• Gerontology
• Thyroid Research

Background:

• Cross-sectional studies indicate rising serum TSH with age.
• Longitudinal data on TSH changes during aging are lacking.
• It remains unclear if TSH increase signifies healthy aging or subclinical thyroid dysfunction.

Purpose of the Study:

• To longitudinally examine age-related changes in thyroid function.
• To investigate whether increasing TSH in aging is linked to occult thyroid disease.

Main Methods:

• Serum TSH, free T4, and thyroid antibodies were measured in 1100 participants across two surveys (1981 and 1994).
• A reference group of 908 individuals without thyroid disease was established.
• Associations with the CAPZB polymorphism rs10917469 were explored in 781 participants.

Main Results:

• Over 13 years, mean serum TSH increased from 1.49 to 1.81 mU/liter (ΔTSH = 0.32 mU/liter), while mean free T4 remained unchanged.
• The TSH increase was more pronounced in older individuals and those with lower baseline TSH.
• No significant difference in TSH change was observed based on CAPZB genotype.

Conclusions:

• Aging is associated with elevated serum TSH levels without a corresponding change in free T4.
• The observed TSH increase likely results from age-related alterations in the TSH set point or reduced TSH bioactivity.
• Findings suggest that rising TSH in aging does not indicate occult thyroid disease.